Substrate processing method and substrate processing apparatus

Abstract

This substrate processing method is for processing a substrate and comprises: irradiating, in a pulsed manner, an outer peripheral region of the substrate with a plurality of split laser light beams obtained by splitting laser light from a laser head; and irradiating, in a pulsed manner, a central region on the radially inner side of the outer peripheral region with a single laser light beam of the laser light without splitting. This substrate processing apparatus is for processing a substrate and comprises: a substrate holding unit that holds the substrate; a laser irradiation unit that irradiates the substrate held by the substrate holding unit with laser light; and a control unit. The laser irradiation unit comprises a laser head that oscillates the laser light, and an optical system that controls splitting of the laser light from the laser head.

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a substrate processing method in which a laser absorbing layer of a laminated substrate is irradiated with pulsed laser light. In this substrate processing method, the laser absorbing layer is irradiated with laser light from the outer periphery toward the center. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2021 / 131711 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology according to the present disclosure efficiently irradiates a substrate with laser light when processing the substrate with the laser light. [Means for solving the problem]

[0005] One aspect of the present disclosure is a substrate processing method for processing a substrate, the method comprising: branching a laser beam from a laser head in an outer peripheral region of the substrate; and irradiating a plurality of branched laser beams with adjusted radial intervals. While rotating the substrate, Pulsing at the same time and irradiating a central region radially inside the outer circumferential region with pulsed single laser light that does not branch the laser light, wherein the multiple branched laser light beams and the single laser light beam are irradiated by switching between the outer circumferential region and the central region on the same substrate. [Effects of the Invention]

[0006] According to the present disclosure, when a substrate is processed by irradiating it with laser light, the irradiation of the laser light can be carried out efficiently. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side view showing an outline of the configuration of overlapping wafers processed in a wafer processing system. [Figure 2] FIG. 1 is a plan view schematically illustrating an outline of the configuration of a wafer processing system. [Figure 3] 1 is a side view showing an outline of the configuration of a wafer processing apparatus; [Figure 4] FIG. 1 is a plan view showing an outline of the configuration of a wafer processing apparatus. [Figure 5] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light. [Figure 6] FIG. 10 is an explanatory view showing how the first wafer is peeled off from the laser absorption layer. [Figure 7] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light. [Figure 8] 10A and 10B are explanatory diagrams showing how a laser absorption layer is irradiated with laser light. [Figure 9] FIG. 2 is an explanatory diagram showing an outline of the configuration of a laser irradiation unit according to the first embodiment. [Figure 10] FIG. 2 is an explanatory diagram showing an outline of the configuration of a laser scanning unit. [Figure 11] FIG. 10 is an explanatory diagram showing an outline of the configuration of a laser irradiation unit according to a second embodiment. [Figure 12] FIG. 10 is an explanatory diagram showing an outline of the configuration of a laser irradiation unit according to a third embodiment. [Figure 13] FIG. 10 is an explanatory diagram showing an outline of the configuration of a laser irradiation unit according to a fourth embodiment. [Figure 14] FIG. 2 is an explanatory diagram showing an outline of the configuration of a spatial phase modulation unit. [Figure 15] 10A and 10B are explanatory diagrams showing how a laser absorption layer according to another embodiment is irradiated with laser light. [Figure 16] 10A and 10B are explanatory diagrams showing how a laser absorption layer according to another embodiment is irradiated with laser light. DETAILED DESCRIPTION OF THE INVENTION

[0008] In the manufacturing process of semiconductor devices, a device layer formed on the surface of a first semiconductor substrate (hereinafter referred to as "wafer") is transferred to a second wafer in a bonded wafer. This device layer transfer is performed, for example, by using laser lift-off. That is, a laser absorption layer formed between the first wafer and the device layer is irradiated with laser light to peel off the first wafer and the laser absorption layer, and the device layer is transferred to the second wafer.

[0009] In laser lift-off, the overlapped wafer is rotated while the laser beam is moved from the outer side to the inner side in the radial direction, and the laser beam is irradiated in pulses. To achieve uniform peeling of the first wafer and the laser absorption layer across the wafer surface, it is preferable to maintain a constant interval between laser beam irradiations, i.e., a constant pulse interval. However, if the pulse interval is maintained constant, the rotation speed of the overlapped wafer increases as the laser beam moves from the outer side to the inner side in the radial direction. When the rotation speed of the overlapped wafer reaches its upper limit, the interval between the laser beams decreases as the irradiation position of the laser beam moves radially inward, and the laser beams may overlap in the center. Furthermore, if the rotation speed of the overlapped wafer increases in the center, the first wafer may peel off.

[0010] Meanwhile, to improve wafer processing throughput, it has been proposed to split a laser beam into multiple beams and irradiate them simultaneously. While irradiating multiple laser beams simultaneously in this way shortens processing time in the peripheral area, the same spot may be irradiated twice in the central area. Because there is a distance between the split laser beams, irradiating the central area with laser beams may result in the first and second beams overlapping. In such cases, excessive energy is supplied to the laser absorption layer, potentially damaging the device layer due to the heat generated. Furthermore, the laser absorption layer may not be able to absorb all of the laser beam, potentially reaching the device layer and causing damage.

[0011] The technology according to the present disclosure efficiently irradiates a substrate with laser light when processing the substrate. Wafer Processing Equipment A wafer processing system including the above-mentioned 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 designated by the same reference numerals, and redundant description will be omitted.

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

[0013] The first wafer W is a semiconductor wafer such as a silicon substrate. A laser absorbing layer P, a device layer Dw, and a surface film Fw are stacked on the surface Wa of the first wafer W in this order from the surface Wa side. The laser absorbing layer P absorbs laser light irradiated from the laser irradiation unit 110, as described below. The laser absorbing layer P may be, for example, an oxide film (SiO2 film), but is not particularly limited as long as it absorbs laser light. The device layer Dw includes multiple devices. Examples of the surface film Fw include an oxide film (SiO2 film, TEOS film), a SiC film, a SiCN film, or an adhesive. The position of the laser absorbing layer P is not limited to the above embodiment and may be formed, for example, between the device layer Dw and the surface film Fw. The device layer Dw and the surface film Fw may not be formed on the surface Wa. In this case, the laser absorbing layer P is formed on the second wafer S side, and the device layer Ds on the second wafer S side, which will be described later, is transferred to the first wafer W side.

[0014] The second wafer S is a semiconductor wafer such as a silicon substrate. On the surface Sa of the second wafer S, a device layer Ds and a surface film Fs are laminated in this order from the surface Sa side. The device layer Ds and the surface film Fs are the same as the device layer Dw and the surface film Fw of the first wafer W, respectively. The surface film Fw of the first wafer W and the surface film Fs of the second wafer S are bonded. Note that the device layer Ds and the surface film Fs may not be formed on the surface Sa.

[0015] 2, the wafer processing system 1 has a configuration in which a load / unload block 10, a transfer block 20, and a processing block 30 are integrally connected. The load / unload block 10 and the processing block 30 are provided around the transfer block 20. Specifically, the load / unload block 10 is disposed on the negative Y-axis side of the transfer block 20. A wafer processing device 31 (described later) in the processing block 30 is disposed on the negative X-axis side of the transfer block 20, and a cleaning device 32 (described later) is disposed on the positive X-axis side of the transfer block 20.

[0016] The carry-in / out block 10 carries in and out cassettes Ct, Cw, and Cs, each capable of accommodating a plurality of overlapping wafers T, a plurality of first wafers W, and a plurality of second wafers S, for example, between the outside and the block. A cassette mounting table 11 is provided in the carry-in / out block 10. In the illustrated example, a plurality of cassettes, for example, three cassettes Ct, Cw, and Cs, can be freely mounted on the cassette mounting table 11 in a line in the X-axis direction. The number of cassettes Ct, Cw, and Cs mounted on the cassette mounting table 11 is not limited to that in this embodiment and can be determined arbitrarily.

[0017] The transfer block 20 is provided with a wafer transfer device 22 that is movable on a transfer path 21 extending in the X-axis direction. The wafer transfer device 22 has, for example, two transfer arms 23, 23 that hold and transfer the overlapped wafer T, the first wafer W, and the second wafer S. Each transfer arm 23 is movable horizontally, vertically, around a horizontal axis, and around a vertical axis. The configuration of the transfer arm 23 is not limited to this embodiment and may be any configuration. The wafer transfer device 22 is configured to transfer the overlapped wafer T, the first wafer W, and the second wafer S to the cassettes Ct, Cw, and Cs on the cassette mounting table 11, and to a wafer processing device 31 and a cleaning device 32, which will be described later.

[0018] The processing block 30 has a wafer processing apparatus 31 and a cleaning apparatus 32. The wafer processing apparatus 31 irradiates a laser light onto the laser absorption layer P of the first wafer W to separate the first wafer W from the second wafer S. The configuration of the wafer processing apparatus 31 will be described later.

[0019] The cleaning device 32 cleans the surface of the laser absorbing layer P formed on the surface Sa of the second wafer S separated in the wafer processing device 31. For example, a brush is brought into contact with the surface of the laser absorbing layer P to scrub the surface. A pressurized cleaning liquid may be used to clean the surface. The cleaning device 32 may also be configured to clean the back surface Sb of the second wafer S as well as the surface Sa.

[0020] The wafer processing system 1 described above is provided with a control device 40 as a control unit. The control device 40 is, for example, a computer, and has a program storage unit (not shown). The program storage unit stores a program for controlling the processing of the overlapped wafer T in the wafer processing system 1. The program storage unit also stores a program for controlling the operation of drive systems such as the various processing devices and transport devices described above to realize wafer processing, which will be described later, in the wafer processing system 1. The program may be recorded on a computer-readable storage medium H and installed into the control device 40 from the storage medium H.

[0021] Next, the above-mentioned wafer processing apparatus 31 will be described.

[0022] 3 and 4, the wafer processing apparatus 31 has a chuck 100 as a substrate holder that holds the overlapped wafer T on its upper surface. The chuck 100 holds the entire back surface Sb of the second wafer S by suction. The chuck 100 may also hold a portion of the back surface Sb by suction. The chuck 100 is provided with lifting pins (not shown) for supporting the overlapped wafer T from below and lifting it up and down. The lifting pins are inserted into through holes (not shown) formed through the chuck 100 and are configured to be freely raised and lowered.

[0023] The chuck 100 is supported by a slider table 102 via an air bearing 101. A rotation mechanism 103 is provided on the underside of the slider table 102. The rotation mechanism 103 incorporates, for example, a motor as a drive source. The chuck 100 is configured to be rotatable around the θ-axis (vertical axis) via the air bearing 101 by the rotation mechanism 103. The slider table 102 is configured to be movable along a rail 105 provided on a base 106 and extending in the Y-axis direction by a movement mechanism 104 provided on the underside of the slider table 102. The drive source of the movement mechanism 104 is not particularly limited, but a linear motor, for example, is used.

[0024] A laser irradiation unit 110 is provided above the chuck 100. The laser irradiation unit 110 has a laser head 111, an optical system 112, and a lens 113. The lens 113 may be configured to be movable up and down by an elevator mechanism (not shown).

[0025] The laser head 111 has a laser oscillator (not shown) that oscillates a laser beam in pulses. This laser beam is a so-called pulsed laser. In this embodiment, the laser beam is a CO2 laser beam, and the wavelength of the CO2 laser beam is, for example, 8.9 μm to 11 μm. The laser head 111 may also have other devices besides the laser oscillator, such as an amplifier.

[0026] The optical system 112 has an optical element (not shown) that controls the intensity and position of the laser light, and an attenuator (not shown) that attenuates the laser light to adjust the output. The optical system 112 also controls the branching of the laser light. The configuration for controlling the branching of the laser light will be described later.

[0027] The lens 113 irradiates the laser beam onto the overlapped wafer T held by the chuck 100. The laser beam emitted from the laser irradiation unit 110 passes through the first wafer W and is irradiated onto the laser absorption layer P.

[0028] A transfer pad 120 is provided above the chuck 100. The transfer pad 120 is configured to be freely raised and lowered by an elevation mechanism (not shown). The transfer pad 120 has an adsorption surface for the first wafer W. The transfer pad 120 transfers the first wafer W between the chuck 100 and the transfer arm 23. Specifically, after the chuck 100 is moved below the transfer pad 120 (to a position for transfer with the transfer arm 23), the transfer pad 120 adsorbs and holds the back surface Wb of the first wafer W and separates it from the second wafer S. The separated first wafer W is then transferred from the transfer pad 120 to the transfer arm 23 and removed from the wafer processing apparatus 31.

[0029] Next, a description will be given of wafer processing performed using the wafer processing system 1 configured as described above. In this embodiment, a first wafer W and a second wafer S are bonded together in a bonding device (not shown) external to the wafer processing system 1 to form an overlapped wafer T in advance.

[0030] First, a cassette Ct containing a plurality of overlapping wafers T is placed on the cassette placement table 11 of the carry-in / out block 10.

[0031] Next, the overlapped wafer T is removed from the cassette Ct by the wafer transfer device 22 and transferred to the wafer processing device 31. In the wafer processing device 31, the overlapped wafer T is transferred from the transfer arm 23 to the chuck 100 and is held by suction on the chuck 100. Next, the moving mechanism 104 moves the chuck 100 to a processing position. This processing position is a position where the laser irradiation unit 110 can irradiate the overlapped wafer T (laser absorption layer P) with laser light.

[0032] 5, pulsed laser light L (CO2 laser light) is irradiated from the laser irradiation unit 110 onto the laser absorbing layer P, more specifically onto the interface between the laser absorbing layer P and the first wafer W. At this time, the laser light L passes through the first wafer W from the rear surface Wb side of the first wafer W and is absorbed in the laser absorbing layer P. Then, this laser light L causes peeling at the interface between the laser absorbing layer P and the first wafer W. A specific method of irradiating this laser light L will be described later.

[0033] In this way, the laser light L is irradiated in pulses onto the laser absorbing layer P. When the laser light L is oscillated in pulses, the peak power (maximum intensity of the laser light) can be increased to cause delamination at the interface between the laser absorbing layer P and the first wafer W. As a result, the first wafer W can be properly delaminated from the laser absorbing layer P.

[0034] Next, the chuck 100 is moved to the delivery position by the moving mechanism 104. Then, as shown in FIG. 6(a), the backside Wb of the first wafer W is sucked and held by the transfer pad 120. Thereafter, as shown in FIG. 6(b), while the transfer pad 120 is sucking and holding the first wafer W, the transfer pad 120 is raised to peel the first wafer W from the laser absorption layer P. At this time, because peeling has occurred at the interface between the laser absorption layer P and the first wafer W due to the irradiation of the laser light L as described above, the first wafer W can be peeled from the laser absorption layer P without applying a large load. The first wafer W may also be peeled off by rotating the transfer pad 120 around a vertical axis.

[0035] The delaminated first wafer W is transferred from the transfer pad 120 to the transfer arm 23 of the wafer transfer device 22 and transferred to the cassette Cw on the cassette mounting table 11. The first wafer W transferred from the wafer processing device 31 may be transferred to the cleaning device 32 before being transferred to the cassette Cw, where its delaminated surface, that is, its front surface Wa, may be cleaned. In this case, the first wafer W may be turned over by the transfer pad 120 and then transferred to the transfer arm 23.

[0036] On the other hand, the second wafer S held by the chuck 100 is 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 Sb of the second wafer S may also be cleaned together with the front surface of the laser absorbing layer P. Alternatively, separate cleaning units may be provided to clean the front surface of the laser absorbing layer P and the back surface Sb of the second wafer S, respectively.

[0037] Thereafter, the second wafer S that has been subjected to all the processes is transferred by the wafer transfer device 22 to the cassette Cs on the cassette mounting table 11. In this way, a series of wafer processes in the wafer processing system 1 is completed.

[0038] Next, a method for irradiating the laser light L in the wafer processing apparatus 31 will be described. As will be described later, the laser irradiation unit 110 can branch the laser light L and scan the laser light L. In the following description, scanning the laser light L means moving the laser light L irradiated from the lens 113 of the laser irradiation unit 110 relative to the laser absorption layer P.

[0039] In this embodiment, the overlapped wafer T is rotated and the laser light L is irradiated in pulses while moving from the outer side to the inner side in the radial direction. At this time, if the intervals at which the laser light L is irradiated are constant in order to uniformly peel the first wafer W and the laser absorbing layer P across the wafer surface, the rotation speed of the overlapped wafer T increases as the laser light L moves from the outer side to the inner side in the radial direction. In such a case, the laser light L may overlap in the central region of the laser absorbing layer P. Furthermore, if the rotation speed of the overlapped wafer T becomes too fast in the central region, the first wafer W may peel off during processing. Therefore, the laser light L is irradiated in the outer peripheral region while the overlapped wafer T is rotating, and the laser light L is scanned in the central region while the rotation of the overlapped wafer T is stopped.

[0040] In this embodiment, to improve wafer processing throughput, the laser beam L is split into multiple beams and irradiated simultaneously. Simultaneous irradiation of multiple laser beams L in this manner shortens processing time in the peripheral region, but in the central region, the same location may be irradiated twice with the laser beam. Because there is a distance between the split laser beams L, scanning the central region with the laser beam L may result in the first laser beam L irradiated and the second laser beam L overlapping. In this case, more energy than necessary is supplied to the laser absorption layer P, which may damage the device layer Dw due to the generated heat. Furthermore, the laser absorption layer P may not be able to absorb all of the laser beam L, which may reach the device layer Dw and cause damage. Therefore, to avoid the effect of the distance between the split laser beams L, the laser beam L is irradiated without splitting in the central region.

[0041] As described above, in this embodiment, the irradiation method (optical system 112) of the laser light L is switched between the outer peripheral region and the central region of the laser absorption layer P. The boundary between the outer peripheral region and the central region is, for example, the position where the rotation speed of the chuck 100 reaches an upper limit, and is the limit position where branched laser light L1 and L2, which will be described later, obtained by branching the laser light L do not overlap when the chuck 100 moves from the outer side to the inner side in the radial direction.

[0042] 7 and 8, in the outer peripheral region R1 of the laser absorption layer P, the chuck 100 (superimposed wafer T) is rotated by the rotation mechanism 103, and the chuck 100 is moved in the negative direction of the Y axis by the movement mechanism 104. At this time, the laser beam L from the laser head 111 is branched into multiple beams, for example, two beams, in the laser irradiation unit 110, and the branched laser beams L1 and L2 (hereinafter referred to as "branched laser beams") are simultaneously irradiated in a pulsed manner. The branched laser beams L1 and L2 are fixed without being scanned. Then, in the outer peripheral region R1, two rows of branched laser beams L1 and L2 are irradiated in a spiral from the radially outer side toward the inner side.

[0043] The number of branches into the branched laser beams L1 and L2 is not limited to that in this embodiment, and may be, for example, three or more.

[0044] Furthermore, the radial distance (index pitch) between the branched laser beams L1 and L2 is adjusted in the laser irradiation unit 110, as will be described later. In the outer circumferential region R1, the radial distance between the branched laser beams L1 and L2 is adjusted, and the branched laser beams L1 and L2 are irradiated in a range where they do not affect each other.

[0045] The rotation of the chuck 100 is stopped in the central region R2 of the laser absorption layer P. Then, the laser beam L from the laser head 111 is not branched in the laser irradiation unit 110, and the unbranched laser beam L3 (hereinafter referred to as "single laser beam") is irradiated in pulses. The central region R2 is scanned with this single laser beam L3.

[0046] At this time, as shown in FIG. 7, scanning irradiation of the single laser beam L3 and movement of the chuck 100 in the negative direction of the Y-axis may be repeated in the central region R2. The scanning range of the single laser beam L3 in one scan is limited depending on the performance of the laser scanning unit. For example, if the scanning range is smaller than the central region R2, scanning of the single laser beam L3 is repeated. In the illustrated example, the central region R2 is divided into four scan regions R2a to R2d. Then, after scanning and irradiating the single laser beam L3 in the scan region R2a, the chuck 100 is moved in the negative direction of the Y-axis, and then scanning and irradiating the single laser beam L3 in the scan region R2b. This scanning and irradiation of the single laser beam L3 and movement of the chuck 100 in the negative direction of the Y-axis are repeated to irradiate the entire central region R2 with the single laser beam L3.

[0047] 8, the scanning irradiation of the single laser beam L3 and the movement of the chuck 100 in the negative Y-axis direction may be synchronized in the central region R2. In this way, by moving the chuck 100 in the negative Y-axis direction (indicated by the black arrow in the figure) while scanning and irradiating the single laser beam L3, the entire central region R2 is irradiated with the single laser beam L3.

[0048] In this embodiment, since the two rows of branched laser beams L1 and L2 are irradiated in a spiral pattern, when switching from the branched laser beams L1 and L2 to the single laser beam L3, there is a possibility that a small unirradiated portion where the laser beam is not irradiated will be generated at the boundary between the outer peripheral region R1 and the central region R2 from the position where irradiation of the branched laser beams L1 and L2 is stopped. Therefore, although not shown in detail in Figures 7 and 8, the single laser beam L3 is irradiated at an appropriate index pitch so as to fill in the unirradiated portion, and the single laser beam L3 is also irradiated to this unirradiated portion.

[0049] According to this embodiment, since the peripheral region R1 is simultaneously irradiated with the branched laser beams L1 and L2 at multiple focal points, the throughput of wafer processing can be improved. Also, since the central region R2 is irradiated with the single laser beam L3 at a single focal point, it is possible to prevent the single laser beam L3 from irradiating the same position twice, thereby suppressing damage to the device layer Dw.

[0050] In this embodiment, the branched laser beams L1 and L2 are irradiated spirally onto the outer peripheral region R1, but they may be irradiated concentrically or annularly. In this embodiment, the chuck 100 is rotated to irradiate the outer peripheral region R1 with the branched laser beams L1 and L2. Alternatively, the lens 113 may be moved to rotate the lens 113 relative to the chuck 100. Furthermore, the chuck 100 is moved in the Y-axis direction, but the lens 113 may be moved in the Y-axis direction.

[0051] In addition, in this embodiment, the laser light L (branched laser light L1, L2 and single laser light L3) is irradiated from the radial outside to the inside in the laser absorption layer P, but it may be irradiated from the radial inside to the outside.

[0052] Next, several embodiments will be described regarding the configuration of the laser irradiation unit 110 for realizing the above-described irradiation method of the laser light L. In any of the embodiments, the laser irradiation unit 110 controls the branching of the laser light L from the laser head 111 and also controls the scanning of the laser light L.

[0053] 9, in the laser irradiation unit 110 of the first embodiment, the optical system 112 has a polarization adjustment unit 200, a polarization separation unit 201, a branch generation unit 202, a polarization synthesis unit 203, and a laser scanning unit 204. The polarization adjustment unit 200, the polarization separation unit 201, the branch generation unit 202, the polarization synthesis unit 203, and the laser scanning unit 204 are arranged in this order on the optical path of the laser light L in the optical system 112.

[0054] The polarization adjuster 200 adjusts the polarization of the laser light L from the laser head 111. The polarization adjuster 200 separates and emits P-polarized light and S-polarized light from the light flux of the laser light L. In other words, the polarization adjuster 200 switches between P-polarized light (corresponding to branched laser light L1 and L2 as described later) and S-polarized light (corresponding to single laser light L3 as described later). P-polarized light is linearly polarized light in which the electric field oscillates within the plane of incidence, and S-polarized light is linearly polarized light in which the electric field oscillates perpendicular to the plane of incidence.

[0055] The polarization splitter 201 transmits or reflects the polarized light adjusted by the polarization adjuster 200. When P polarized light is emitted from the polarization adjuster 200, the polarization splitter 201 transmits the P polarized light and directs it to the branching and generating unit 202. When S polarized light is emitted from the polarization adjuster 200, the polarization splitter 201 reflects the S polarized light and directs it to the polarization synthesizing unit 203.

[0056] The branch generation unit 202 branches the P-polarized light transmitted through the polarization separation unit 201 into multiple beams, for example, two beams. The branch generation unit 202 includes an optical element (not shown), and can arbitrarily adjust the radial spacing (index pitch) between the two P-polarized light beams by rotating the optical element. Specifically, the radial spacing between the two P-polarized light beams is adjusted so that the two P-polarized light beams are irradiated in a range of the laser absorption layer P where they do not affect each other.

[0057] The branch generation unit 202 may have any configuration, for example, a DOE (Diffractive Optical Element). The number of branches of P polarized light in the branch generation unit 202 is not limited to that in this embodiment, and may be, for example, three or more.

[0058] The polarization combining unit 203 reflects the S-polarized light reflected by the polarization separating unit 201, and directs it toward the laser scanning unit 204. The polarization combining unit 203 also transmits the multiple P-polarized light beams branched by the branch generating unit 202, and directs them toward the laser scanning unit 204.

[0059] The laser scanning unit 204 controls the scanning of polarized light (laser light L), and for example, a galvanometer is used. As shown in FIG. 10, a plurality of galvanometer mirrors 205 are arranged inside the laser scanning unit 204. An f-θ lens is used as the lens 113. With this configuration, polarized light input to the laser scanning unit 204 is reflected by the galvanometer mirror 205, propagates to the lens 113, and is irradiated onto the laser absorption layer P. Then, by adjusting the angle of the galvanometer mirror 205, the polarized light can be scanned across the laser absorption layer P.

[0060] The optical system 112 has a first optical path A1 and a second optical path A2.

[0061] The first optical path A1 is an optical path that splits the P-polarized light of the laser light L. That is, in the first optical path A1, the P-polarized light is transmitted through the polarization separation unit 201, the P-polarized light is split by the split generation unit 202, and the P-polarized light is transmitted through the polarization synthesis unit 203. Furthermore, the P-polarized light split through the first optical path A1 passes through the laser scanning unit 204, but is not scanned relative to the laser absorption layer P.

[0062] The two branched P-polarized light beams that have passed through the first optical path A1 are irradiated onto the outer peripheral region R1 of the laser absorption layer P. These two P-polarized light beams correspond to the branched laser beams L1 and L2 described above.

[0063] The second optical path A2 is an optical path that does not split the S-polarized light of the laser light L. That is, in the second optical path A2, the S-polarized light is reflected by the polarization separation unit 201, and the S-polarized light is reflected by the polarization synthesis unit 203. Furthermore, the S-polarized light that has passed through the second optical path A2 passes through the laser scanning unit 204 and scans the laser absorption layer P.

[0064] The S-polarized light passes through the second optical path A2 and is scanned and irradiated onto the central region R2 of the laser absorption layer P. This S-polarized light corresponds to the single laser light L3 described above.

[0065] In this embodiment, the P-polarized light of the laser light L is split into split laser light L1 and L2, and the S-polarized light is not split but is instead split into single laser light L3. However, the S-polarized light may be split but the P-polarized light may not be split. That is, the S-polarized light may be passed through the first optical path A1, and the P-polarized light may be passed through the second optical path A2.

[0066] 11 , in the laser irradiation unit 110 of the second embodiment, the optical system 112 has a first mirror 210, a branch generation unit 211, a second mirror 212, and a laser scanning unit 213. The first mirror 210, the branch generation unit 211, the second mirror 212, and the laser scanning unit 213 are arranged in this order on the optical path of the laser light L in the optical system 112.

[0067] The branch generation unit 211 branches the laser light L into a plurality of beams, for example, two beams. The number of beams into which the laser light L is branched in the branch generation unit 211 is not limited to that in this embodiment, and may be, for example, three or more. The configuration of the branch generation unit 211 is similar to the configuration of the branch generation unit 202 in the first embodiment.

[0068] The laser scanning unit 213 controls the scanning of the laser light L, and for example, a galvanometer is used. The configuration of the laser scanning unit 213 is similar to the configuration of the laser scanning unit 204 of the first embodiment.

[0069] The first mirror 210 and the second mirror 212 are configured to be movable relative to the optical path by movement mechanisms 214 and 215, respectively. The first mirror 210 arranged in the optical path reflects the laser light L from the laser head 111 and directs it toward the second mirror 212. Furthermore, the second mirror 212 arranged in the optical path reflects the laser light L and directs it toward the laser scanning unit 216. 213 Direct them towards.

[0070] 11(a), when the first mirror 210 and the second mirror 212 are retracted from the optical path, a first optical path B1 is formed. The first optical path B1 is an optical path that branches the laser light. That is, in the first optical path B1, the laser light L from the laser head 111 is branched by the branch generation unit 211. The laser light L branched through the first optical path B1 passes through the laser scanning unit 213 but does not scan the laser absorption layer P.

[0071] Two laser beams L branched along the first optical path B1 are irradiated onto the outer peripheral region R1 of the laser absorption layer P. These two laser beams L correspond to the branched laser beams L1 and L2 described above.

[0072] 11(b), when the first mirror 210 and the second mirror 212 are arranged in the optical path, a second optical path B2 is formed. The second optical path B2 is an optical path that does not branch the laser light L. That is, in the second optical path B2, the laser light L from the laser head 111 is reflected by the first mirror 210 and further reflected by the second mirror 212. The laser light L that has passed through the second optical path B2 passes through the laser scanning unit 213 and scans the laser absorption layer P.

[0073] The laser light L that has passed through the second optical path B2 is scanned and irradiated onto the central region R2 of the laser absorption layer P. This laser light L corresponds to the single laser light L3 described above.

[0074] In this embodiment, the first mirror 210 and the second mirror 212 are configured to be movable forward and backward, but the configuration for forming the first optical path B1 and the second optical path B2 is not limited to this. For example, the first mirror 210 and the second mirror 212 may each be switched between reflection and transmission using a voltage or the like. Alternatively, for example, the first mirror 210 and the second mirror 212 may be omitted, and the branch generation unit 211 may be configured to be movable relative to the optical path.

[0075] According to the first and second embodiments described above, the optical system 112 has the first optical paths A1 and B1 and the second optical paths A2 and B2, so that it is possible to control the branching of the laser light L. Furthermore, the scanning of the laser light L can be controlled by the laser scanning units 204 and 213, such as galvanometers. Therefore, it is possible to improve the throughput of wafer processing and to prevent the single laser light L3 from being irradiated twice at the same position.

[0076] As shown in Fig. 12, in the laser irradiation unit 110 of the third embodiment, the lens 113 includes a fixed lens 113a and a scanning lens 113b. In the laser irradiation units 110 of the first and second embodiments, the optical system 112 has two optical paths, and the laser light L is irradiated from one lens 113. In contrast, in the laser irradiation unit 110 of the third embodiment, the optical system 112 has two optical paths, and the laser light L is irradiated from lenses 113a and 113b corresponding to the respective optical paths. Note that, although the following description will be given of a case where the optical system 112 of the third embodiment is the optical system 112 of the first embodiment, it may also be the optical system 112 of the second embodiment.

[0077] The fixed lens 113a is provided corresponding to the first optical path A1. The fixed lens 113a irradiates a predetermined position with the P-polarized light without scanning it. The P-polarized light (branched laser beams L1, L2) branched through the first optical path A1 is irradiated onto the outer peripheral region R1 of the laser absorption layer P via the fixed lens 113a without being scanned. At this time, the chuck 100 is rotated and moved in the negative direction of the Y-axis.

[0078] The scanning lens 113b is provided corresponding to the second optical path A2. An f-θ lens is used for the scanning lens 113b, and the S-polarized light is scanned by the laser scanning unit 204. Then, the S-polarized light (single laser light L3) that has passed through the second optical path A2 is scanned and irradiated onto the central region R2 of the laser absorption layer P via the scanning lens 113b.

[0079] In the third embodiment, the laser scanning unit 204 is not provided on the first optical path A1, but is provided on the second optical path A2.

[0080] According to the third embodiment described above, it is possible to obtain the same effects as those of the first and second embodiments. That is, the branching of the laser beam L is controlled by the two optical paths A1 and A2, and the scanning of the laser beam L is controlled by the laser scanning unit 204, for example, a galvanometer. Therefore, it is possible to improve the throughput of wafer processing and to prevent the single laser beam L3 from being irradiated twice at the same position.

[0081] Here, when the P-polarized light (branched laser beams L1, L2) is irradiated onto the outer peripheral region R1 of the laser absorption layer P, the P-polarized light is fixed and not scanned. In such a case, if the laser scanning unit 204 is used for a long period of time with the operation thereof stopped, the lens 113 corresponding to the laser scanning unit 204 may be damaged. In this regard, in this embodiment, the laser scanning unit 204 is not provided on the first optical path A1, and a fixed lens 113a separate from the scanning lens 113b is provided. Therefore, the P-polarized light does not pass through the fixed lens 113a, and damage to the fixed lens 113a can be prevented.

[0082] 13, in the laser irradiation unit 110 of the fourth embodiment, the optical system 112 has a spatial phase modulation unit 220 and a laser scanning unit 221. The spatial phase modulation unit 220 and the laser scanning unit 221 are arranged in this order on the optical path C of the laser light L in the optical system 112.

[0083] The laser scanning unit 221 controls the scanning of the laser light L, and for example, a galvanometer is used. The configuration of the laser scanning unit 221 is similar to the configuration of the laser scanning unit 204 of the first embodiment.

[0084] The spatial phase modulation unit 220 controls the phase of the laser light L, thereby controlling the branching of the laser light L. For example, a deformable mirror is used for the spatial phase modulation unit 220. As shown in FIG. 14, a plurality of mirrors 222 are arranged inside the spatial phase modulation unit 220. The branching of the laser light L is controlled by individually and programmably controlling the up and down movements of these plurality of mirrors 222.

[0085] 14(a), by controlling the vertical arrangement of the multiple mirrors 222, the input laser light L is branched and branched laser light L1 and L2 are output. These branched laser light L1 and L2 are irradiated onto the outer peripheral region R1 of the laser absorption layer P as described above.

[0086] 14(b), when the arrangement of the multiple mirrors 222 is controlled to be flat, the input laser light L is not branched, and a single laser light L3 is output. This single laser light L3 is irradiated onto the central region R2 of the laser absorption layer P as described above.

[0087] In this embodiment, a deformable mirror is used in the spatial phase modulation unit 220, but the configuration of the spatial phase modulation unit 220 is not limited to this. For example, LCOS (Liquid Crystal Silicon) may be used in the spatial phase modulation unit 220. LCOS can control the focal position and phase of the laser light L, and can also control the shape and number of branches of the laser light L.

[0088] According to the above-described fourth embodiment, unlike the first to third embodiments, there is only one optical path C in the optical system 112, but the branching of the laser light L can be controlled by the spatial phase modulation unit 220. Furthermore, the scanning of the laser light L can be controlled by, for example, a galvanometer, which is the laser scanning unit 221. Therefore, the throughput of wafer processing can be improved, and it is possible to prevent the single laser light L3 from being irradiated twice at the same position.

[0089] In the above embodiment, the central region R2 of the laser absorption layer P is irradiated by scanning with the single laser L3 while the rotation of the chuck 100 (superimposed wafer T) is stopped, but the single laser light L3 may also be irradiated by scanning while rotating the superimposed wafer T as shown in FIG. 15.

[0090] For example, in the above embodiment, the rotation of the overlapped wafer T is stopped in the central region R2 to prevent the laser beams L from overlapping in the central region R2 due to the rotation speed of the overlapped wafer T or to prevent the first wafer W from peeling off during processing while it is rotating. In this regard, if there is no risk of the laser beams L overlapping or the first wafer W from peeling off in the central region R2, it is not necessary to stop the rotation of the overlapped wafer T in the central region R2. In this case, the rotation speed of the overlapped wafer T in the central region R2 may be lower than that in the peripheral region R1.

[0091] As in the above-described embodiment shown in Figures 7 and 8, when switching from the branched laser beams L1 and L2 to the single laser beam L3 at the boundary between the peripheral region R1 and the central region R2, the single laser beam L3 is irradiated at an appropriate index pitch so as to be continuous with the irradiation points of the branched laser beams L1 and L2.

[0092] 16, the single laser beam L3 may be rotationally scanned while the rotation of the overlapped wafer T is stopped. Specifically, for example, the laser scanning units 204, 213, and 221, such as the galvanometer mirror 205, rotates and scans the single laser beam L3 using a rotation mechanism (not shown).

[0093] 7, 8, and 15, when switching from the branched laser beams L1 and L2 to the single laser beam L3 at the boundary between the peripheral region R1 and the central region R2, the single laser beam L3 is irradiated at an appropriate index pitch so as to be continuous with the irradiation points of the branched laser beams L1 and L2. Furthermore, when switching from the branched laser beams L1 and L2 to the single laser beam L3, a small unirradiated portion where the laser beams L1 and L2 are not irradiated may occur from the irradiation stop position of the branched laser beams L1 and L2. The single laser beam L3 is irradiated so as to fill this unirradiated portion. In such a case, the single laser beam L3 may not be continuous with the irradiation point of the branched laser beam L1 or the branched laser beam L2.

[0094] 15 and 16, the outer peripheral region R1 is irradiated with the branched laser beams L1 and L2 in a spiral pattern, but they may also be irradiated with concentric ring patterns. Similarly, the central region R2 is irradiated with the single laser beam L3 in a spiral pattern, but they may also be irradiated with concentric ring patterns.

[0095] In the above embodiments, galvanometers are used for the laser scanning units 204, 213, and 221 that scan the single laser beam L3, but the configuration for scanning the single laser beam L3 is not limited to this. For example, it is sufficient if the irradiation point of the laser beam irradiated from the lens can be scanned or rotated in a direction opposite to the Y-axis direction. Specifically, for example, the lens portion scans the laser beam using a scanning mechanism or a rotating mechanism.

[0096] In the above embodiment, the irradiation method of the laser light L on the laser absorption layer P (laser irradiation target) is switched between the outer peripheral region R1 and the central region R2, but the switching method is not limited to this. The irradiation region of the branched laser beams L1 and L2 and the irradiation region of the unbranched single laser beam L3 can be set arbitrarily.

[0097] In the above embodiment, the method of irradiating laser light L of the present disclosure is applied when performing laser lift-off to peel the first wafer W from the laser absorption layer P, but the wafer processing to which the method is applicable is not limited to this.

[0098] In the manufacturing process of semiconductor devices, a modified layer is formed inside a silicon substrate of a wafer having a plurality of devices such as electronic circuits formed on its surface by irradiating the silicon substrate with laser light along the surface direction, and the wafer is then separated at the modified layer to thin the wafer. A YAG laser beam is used as the laser light. The laser light irradiation method of the present disclosure can also be applied to forming such a modified layer. Furthermore, the laser light irradiation method of the present disclosure can also be applied to techniques for modifying the surface of a wafer and for planarizing the surface of a wafer.

[0099] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0100] 31 Wafer processing equipment 40 Control device 100 Chuck 110 Laser irradiation unit 111 Laser Head 112 Optical system T Polymerized Wafer W First wafer S Second wafer

Claims

1. A substrate processing method for processing a substrate, comprising: branching a laser beam from a laser head onto an outer peripheral region of the substrate, and simultaneously irradiating the substrate with a plurality of branched laser beams, the radial intervals of which are adjusted, in a pulsed manner while rotating the substrate; and irradiating a central region radially inside the outer circumferential region with a single laser beam in a pulsed manner without branching the laser beam, A substrate processing method, comprising switching between irradiating the peripheral region and the central region of the same substrate with the plurality of branched laser beams and the single laser beam.

2. A substrate processing method as described in claim 1, wherein the single laser light is scanned and irradiated in the central region while the rotation of the substrate is stopped.

3. The branched laser beam is irradiated from a fixed lens, The substrate processing method according to claim 2 , wherein the single laser beam is irradiated from a scanning lens.

4. The optical system for controlling the branching of the laser light includes: a first optical path for branching the laser light; a second optical path that does not branch the laser light, the laser beam passes through the first optical path in the outer peripheral region, and the plurality of branched laser beams are irradiated; 4. The substrate processing method according to claim 1, wherein the central region is irradiated with the single laser beam by passing the laser beam through the second optical path.

5. The optical system comprises: a polarization adjuster that adjusts the polarization of the laser light; a polarization splitter that transmits or reflects the polarized light adjusted by the polarization adjuster; a branch generation unit that branches the polarized light transmitted through the polarization separation unit; a polarization synthesis unit that reflects the polarized light reflected by the polarization separation unit or transmits the polarized light branched by the branch generation unit, the first optical path is an optical path through which polarized light is transmitted by the polarization separation unit, polarized light is branched by the branch generation unit, and polarized light is transmitted by the polarization synthesis unit, 5. The substrate processing method according to claim 4, wherein the second optical path is an optical path in which polarized light is reflected by the polarization separation unit and polarized light is reflected by the polarization synthesis unit.

6. The optical system comprises: a branch generating unit provided on an optical path of the laser beam and branching the laser beam; a first mirror configured to be freely moved forward and backward with respect to the optical path upstream of the branch generation unit; a second mirror configured to be freely moved forward and backward with respect to the optical path downstream of the branch generation unit, the first optical path is an optical path in which the laser beam is branched by the branch generation unit in a state in which the first mirror and the second mirror are retracted from the optical path, 5. The substrate processing method according to claim 4, wherein the second optical path is an optical path in which the laser light is reflected by the first mirror and the second mirror while the first mirror and the second mirror are inserted onto the optical path.

7. the optical system for controlling the branching of the laser beam includes a spatial phase modulation unit for the laser beam, 3. The substrate processing method according to claim 1, wherein the spatial phase modulation unit controls a phase of the laser light, thereby controlling branching of the laser light.

8. the substrate is a laminated substrate in which a first substrate having a laser absorption layer formed on a surface thereof and a second substrate are bonded together, 3. The substrate processing method according to claim 1, wherein the laser light is absorbed by the laser absorption layer.

9. A substrate processing apparatus for processing a substrate, a substrate holder for holding the substrate; a laser irradiation unit that irradiates the substrate held by the substrate holding unit with laser light; a rotation mechanism that rotates the substrate holder; a control unit, The laser irradiation unit a laser head that oscillates the laser light; an optical system that splits the laser light from the laser head, The control unit branching the laser beam in an outer peripheral region of the substrate, and controlling the plurality of branched laser beams, the radial intervals of which are adjusted, to be simultaneously irradiated in a pulsed manner while rotating the substrate; controlling the laser beam to be irradiated in a pulsed manner in a central region radially inside the outer circumferential region; and controlling irradiation of the same substrate by switching between the plurality of branched laser beams and the single laser beam in the outer peripheral region and the central region.

10. A laser scanning unit for scanning the single laser beam, The substrate processing apparatus according to claim 9 , wherein the control unit controls the single laser light to be scanned and irradiated in the central region while the rotation of the substrate is stopped.

11. a fixed lens for irradiating the branched laser beam; The substrate processing apparatus according to claim 10 , further comprising: a scanning lens for scanning and irradiating the single laser beam.

12. The optical system comprises: a first optical path for branching the laser light; a second optical path that does not branch the laser light, The control unit controlling the laser beam to pass through the first optical path in the outer peripheral region and irradiate the plurality of branched laser beams; 12. The substrate processing apparatus according to claim 9, further comprising: controlling the laser light to pass through the second optical path in the central region and irradiate the central region with the single laser light.

13. The optical system comprises: a polarization adjuster that adjusts the polarization of the laser light; a polarization splitter that transmits or reflects the polarized light adjusted by the polarization adjuster; a branch generation unit that branches the polarized light transmitted through the polarization separation unit; a polarization synthesis unit that reflects the polarized light reflected by the polarization separation unit or transmits the polarized light branched by the branch generation unit, the first optical path is an optical path through which polarized light is transmitted by the polarization separation unit, polarized light is branched by the branch generation unit, and polarized light is transmitted by the polarization synthesis unit, The substrate processing apparatus according to claim 12 , wherein the second optical path is an optical path in which polarized light is reflected by the polarization separation unit and polarized light is reflected by the polarization synthesis unit.

14. The optical system comprises: a branch generating unit provided on an optical path of the laser beam and branching the laser beam; a first mirror configured to be freely moved forward and backward with respect to the optical path upstream of the branch generation unit; a second mirror configured to be freely moved forward and backward with respect to the optical path downstream of the branch generation unit, the first optical path is an optical path in which the laser beam is branched by the branch generation unit in a state in which the first mirror and the second mirror are retracted from the optical path, 13. The substrate processing apparatus according to claim 12, wherein the second optical path is an optical path in which the laser light is reflected by the first mirror and the second mirror while the first mirror and the second mirror are inserted onto the optical path.

15. the optical system includes a spatial phase modulation unit for the laser light, The substrate processing apparatus according to claim 9 , wherein the control unit controls the branching of the laser light by controlling the phase of the laser light with the spatial phase modulation unit.

16. the substrate is a laminated substrate in which a first substrate having a laser absorption layer formed on a surface thereof and a second substrate are bonded together, The substrate processing apparatus according to claim 9 , wherein the laser light is absorbed by the laser absorption layer.

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