Method for separating bonded substrate and method for manufacturing semiconductor device

Abstract

To facilitate peeling of a second substrate from a first substrate while suppressing damage to the first substrate in a bonded substrate.SOLUTION: In a peeling method of a bonded substrate for peeling a second substrate from the bonded substrate (10) in which a first substrate (11) and a second substrate (12) supporting the first substrate are bonded, a laser beam (L) is condensed inside the second substrate to form a modified portion (21) in the second substrate, and stress is generated in a direction in which the second substrate is separated from the first substrate.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for separating a bonded substrate and a method for manufacturing a semiconductor device. [Background technology]

[0002] In the manufacture of semiconductor devices to be incorporated into various electronic devices, devices are formed in each of a plurality of device regions defined by planned division lines (streets) on a wafer, and the wafer is then divided along the planned division lines to produce a plurality of individual device chips. To reduce the size and weight of the device chips, the wafer is thinned before being divided into device chips. For example, the device side of the wafer, on which the devices are formed, is held on a chuck table, and a rotating grinding tool (grinding wheel) is pressed against the back side of the wafer to grind and thin the back side of the wafer.

[0003] When grinding a wafer using the method described above, a protective member such as a support substrate is placed facing the front side of the wafer and fixed to the wafer via a bonding resin or the like. In other words, the wafer and support substrate are bonded together to form a bonded substrate, and the support substrate is supported on a chuck table to process the wafer. This prevents excessive load from being applied to the wafer or device when a force is applied pressing the grinding tool against the back side of the wafer, preventing damage.

[0004] After processing the wafer, the support substrate is peeled off from the wafer. If a strong force is applied when peeling off the support substrate, the wafer, which has been thinned by grinding, may be damaged. One example of a measure to prevent such wafer damage is to fix the wafer and support substrate together using an ultraviolet-curable resin that hardens when irradiated with ultraviolet light when forming a bonded substrate, and then irradiate the resin with ultraviolet light to reduce the bonding strength when peeling off the support substrate from the wafer.

[0005] In some cases, the support substrate adheres tightly to the wafer, making it difficult to easily separate the support substrate from the wafer by simply curing the resin as described above. Furthermore, there are restrictions on the type of resin that can be used to secure the wafer and support substrate, making it impossible to harden the resin as described above during separation. As a solution to such problems, as disclosed in Patent Document 1, a method is known in which a laser beam is focused on the resin that secures the wafer and support substrate, and a portion of the resin is removed by ablation processing, reducing the bonding strength, thereby separating the support substrate from the wafer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2023-082761 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when the thickness of the bonding resin is thin, if a laser beam is focused on the resin in order to facilitate peeling of the support substrate, the laser beam may damage the wafer.

[0008] An object of the present disclosure is to provide a method for peeling a bonded substrate in which a first substrate and a second substrate are bonded together, which facilitates peeling of a second substrate from a first substrate while suppressing damage to the first substrate caused by a laser beam, and a method for manufacturing a semiconductor device. [Means for solving the problem]

[0009] One aspect of the present disclosure is a method for peeling a bonded substrate, which peels a second substrate from a bonded substrate formed by bonding a first substrate to a second substrate supporting the first substrate, and is characterized by focusing a laser beam inside the second substrate to form a modified portion in the second substrate, thereby generating stress in a direction that causes the second substrate to move away from the first substrate.

[0010] When forming the modified portion on the second substrate, it is preferable to focus the laser beam on the first substrate side from the center of the second substrate in the thickness direction.

[0011] The second substrate may include a first region and a second region separated in a direction intersecting the surface of the second substrate facing the first substrate, and in the first region, the laser beam may be focused inside the second substrate on the first substrate side of the center of the thickness direction of the second substrate, and in the second region, the laser beam may be focused inside the second substrate on the opposite side of the first substrate from the center of the thickness direction of the second substrate.

[0012] One aspect of the present disclosure is a method for manufacturing a semiconductor device, comprising: a processing step of processing a first substrate of a bonded substrate formed by bonding a first substrate and a second substrate supporting the first substrate; and a peeling step of peeling the second substrate from the bonded substrate processed in the processing step, wherein the peeling step is characterized by focusing a laser beam inside the second substrate to form a modified portion in the second substrate and generating stress in a direction that causes the second substrate to move away from the first substrate.

[0013] The processing step may include a singulation step of singulating the first substrate.

[0014] In the peeling step, the laser beam may be focused on the first substrate side from the center of the second substrate in the thickness direction.

[0015] The second substrate may include a first region and a second region separated in a direction intersecting the surface of the second substrate, and the peeling step may focus a laser beam in the first region inside the second substrate on the first substrate side of the center of the thickness direction of the second substrate, and focus a laser beam in the second region inside the second substrate on the opposite side of the first substrate from the center of the thickness direction of the second substrate.

[0016] In each of the embodiments of the method for peeling a bonded substrate and the method for manufacturing a semiconductor device, the first region and the second region extend, for example, in a first direction parallel to the surface of the second substrate, and are alternately arranged along a second direction parallel to the surface of the second substrate and intersecting the first direction.

[0017] In each of the embodiments of the method for peeling off a bonded substrate and the method for manufacturing a semiconductor device, it is preferable that the first substrate has a device surface on which a device is formed, the second substrate is a support substrate, and the device surface is bonded facing the support substrate. [Effects of the Invention]

[0018] According to the method for peeling off a bonded substrate and the method for manufacturing a semiconductor device disclosed herein, in a bonded substrate in which a first substrate and a second substrate are bonded together, the second substrate can be easily peeled off from the first substrate while suppressing damage to the first substrate caused by a laser beam. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. [Figure 2] FIG. 2 is a cross-sectional view of a bonded substrate. [Figure 3] FIG. 1 is a diagram illustrating an outline of a laser processing device. [Figure 4] 1A and 1B are cross-sectional views showing a first embodiment of a method for peeling a bonded substrate. [Figure 5] 1A and 1B are cross-sectional views showing a first embodiment of a method for peeling a bonded substrate. [Figure 6] 10A and 10B are cross-sectional views showing a second embodiment of a method for peeling a bonded substrate. [Figure 7] FIG. 10 is a plan view showing an example of the arrangement of the first region and the second region in the second embodiment. [Figure 8] FIG. 10 is a plan view showing an example of the arrangement of the first region and the second region in the second embodiment. [Figure 9] 10 is a cross-sectional view showing an example of the arrangement of the first region and the second region when the first substrate is divided into individual pieces in a processing step. FIG. [Figure 10] FIG. 10 is a cross-sectional view showing a third embodiment of the method for peeling off bonded substrates. DETAILED DESCRIPTION OF THE INVENTION

[0020] The bonding substrate peeling method and semiconductor device manufacturing method of the present disclosure will be described below with reference to the accompanying drawings. The Z-axis direction shown in each drawing is the thickness direction of the bonding substrate 10. The X-axis direction and the Y-axis direction are each perpendicular to the Z-axis direction, and are perpendicular to each other.

[0021] As shown in Fig. 1, bonded substrate 10 is formed by bonding a first substrate 11 and a second substrate 12. First substrate 11 is, for example, a disk-shaped semiconductor wafer made of silicon or the like, and has a device surface 13 and a back surface 14 as both surfaces in the thickness direction. On device surface 13 of first substrate 11, a plurality of device regions are formed, partitioned by grid-like division lines 15 extending in the X-axis direction and the Y-axis direction, and devices 16 are formed in each device region. Devices 16 are, for example, semiconductor devices such as ICs (Integrated Circuits).

[0022] The bonded substrate peeling method of the present disclosure is highly useful when the devices 16 formed on the first substrate 11 are semiconductor devices, i.e., when applied to the manufacture of semiconductor devices, but the material of the first substrate 11 and the type and arrangement of the devices 16 are not limited to those described above. For example, the first substrate 11 may be made of resin, ceramics, metal, etc. The bonded substrate peeling method of the present disclosure is also applicable when the first substrate 11 is a material wafer or the like on which no devices are formed.

[0023] The second substrate 12 is a disk-shaped member and has a first surface 17 facing the first substrate 11 and a second surface 18 facing the opposite side of the first substrate 11. The second substrate 12 is formed of a material such as glass, silicon, or ceramics, but the material is not limited as long as it is possible to form a modified portion (described later). The diameter of the second substrate 12 is equal to or slightly larger than the diameter of the first substrate 11. The second substrate 12 functions as a support substrate that supports the first substrate 11 having the plurality of devices 16.

[0024] Bonded substrate 10 is constructed by stacking and fixing second substrate 12 to first substrate 11. As shown in Fig. 2, in bonded substrate 10, second substrate 12 is fixed to the device surface 13 side of first substrate 11, and first substrate 11 and second substrate 12 are bonded via bonding layer 19.

[0025] The bonding layer 19 is, for example, a sheet containing an ultraviolet-curable resin. The bonding layer 19 is formed by sandwiching an uncured resin sheet between the device surface 13 of the first substrate 11 and the first surface 17 of the second substrate 12, and the first substrate 11 and the second substrate 12 are bonded together by the adhesiveness of the resin contained in the bonding layer 19. Note that the bonding layer 19 is not limited to the above-described form and may be a thermoplastic resin or various other resins, a tape with a glue layer, an adhesive, or the like.

[0026] Alternatively, unlike the bonded substrate 10 shown in the figure, a bonded substrate may be configured such that the facing portions of the first substrate 11 and the second substrate 12 are directly bonded together without the bonding layer 19. For example, one or both of the device surface 13 of the first substrate 11 and the first surface 17 of the second substrate 12 are subjected to a hydrophilic treatment by contacting them with plasma generated under atmospheric pressure, and then the device surface 13 of the first substrate 11 and the first surface 17 of the second substrate 12 are brought face to face and bonded together. Hydrogen bonds are formed between the first substrate 11 and the second substrate 12 via hydroxyl groups formed by the hydrophilic treatment of at least one of the facing surfaces of the first substrate 11 and the second substrate 12, thereby bonding the first substrate 11 and the second substrate 12 together. The amount of hydroxyl groups varies depending on the strength of the hydrophilic treatment, and the bonding strength between the first substrate 11 and the second substrate 12 also varies. By heating the bonded substrate, in which first substrate 11 and second substrate 12 are bonded, to a predetermined first temperature, a dehydration condensation reaction occurs at the bonded portion, improving the adhesion (bonding strength) between first substrate 11 and second substrate 12. Furthermore, by heating the bonded substrate, in which first substrate 11 and second substrate 12 are bonded, to a predetermined second temperature higher than the first temperature, bubbles are generated at the bonding interface between first substrate 11 and second substrate 12, making it easier to peel second substrate 12 from first substrate 11. The method for peeling bonded substrates of the present disclosure can also be applied to bonded substrates of this type.

[0027] In the method for manufacturing a semiconductor device according to the present disclosure, the bonded substrate 10 configured as described above is subjected to processing steps to manufacture devices 16. The processing steps include a grinding step in which the first substrate 11 is ground to a predetermined thickness, and a singulation step in which the first substrate 11 is divided along the planned division lines 15 to divide into a plurality of devices 16. When performing these processing steps, the bonded substrate 10 is held so that the Z-axis direction is the up-down direction, and the X-axis and Y-axis directions are horizontal.

[0028] The grinding process is performed using a grinding device (not shown). The bonded substrate 10 is held on a holding table included in the grinding device. The bonded substrate 10 is placed on the holding surface of the holding table with the second surface 18 of the second substrate 12 facing downward, and is held on the holding table with the back surface 14 of the first substrate 11 facing upward (the side opposite the holding table). A grinding unit positioned above the holding table has a disk-shaped grinding wheel at the lower end of a spindle extending vertically, and grinding stones are arranged in a ring shape on the underside of the grinding wheel. The spindle is rotated and the grinding unit is lowered, and the rotated grinding stone is pressed against the back surface 14 of the first substrate 11. At this time, the holding table is rotated, and the bonded substrate 10 on the holding table is also rotated. In this way, the rotated grinding stone is pressed against the back surface 14 of the rotated first substrate 11, thereby grinding the back surface 14 of the first substrate 11.

[0029] The second substrate 12 fixed to the device surface 13 side of the first substrate 11 is held on a holding table, and the second substrate 12 bears the load applied to the bonded substrate 10 from the grinding wheel, thereby making it possible to grind the back surface 14 of the first substrate 11 without damaging the devices 16. In addition, the second substrate 12 covering the device surface 13 of the first substrate 11 can prevent processing debris and the like generated during the grinding process from adhering to the devices 16. Furthermore, since the second substrate 12 is fixed to the first substrate 11 that has been thinned by grinding, the rigidity of the first substrate 11 can be ensured.

[0030] The singulation process is performed using a cutting device or the like (not shown). When the singulation process is performed using a cutting device, the bonded substrate 10 is held on a holding table provided in the cutting device. As in the grinding process described above, the bonded substrate 10 is held on the holding table with the second surface 18 of the second substrate 12 placed on the holding surface of the holding table and the back surface 14 of the first substrate 11 facing upward. A cutting unit positioned above the holding table has an annular cutting blade at the tip of a horizontally extending spindle. The spindle is rotated and the cutting unit is lowered, causing the rotated cutting blade to cut into the first substrate 11. The cutting blade cutting position is set on the planned division line 15 of the first substrate 11, and the holding table and the cutting unit are moved relatively in the horizontal direction along the planned division line 15 to form a processing groove 20 (see FIG. 9 ) that divides the first substrate 11 along the planned division line 15. By forming grooves 20 along the respective dividing lines 15 arranged in a grid pattern, the plurality of devices 16 formed on the first substrate 11 are separated into individual pieces.

[0031] Although Figure 9 shows the processed groove 20 in the form of a full-cut groove that penetrates the first substrate 11 in the thickness direction, it is also possible to form a bottomed half-cut groove that is deep enough to reach partway through the thickness direction of the first substrate 11 as the processed groove, and then use the half-cut groove as the starting point for dividing the first substrate 11 to individualize the devices 16.

[0032] Alternatively, in the singulation process, a laser processing device may be used to focus a laser beam inside the first substrate 11 (at a position along the planned division line 15) to form a modified portion, and the first substrate 11 may be divided using the modified portion as the starting point for division to individualize the devices 16.

[0033] The processing step may include both a grinding step and a singulation step, or only one of them. Furthermore, the processing step may include processing other than grinding or singulation (e.g., polishing) on ​​the bonded substrate 10. Furthermore, in addition to processing, the bonded substrate 10 may also be subjected to various processes such as inspection, measurement, and transportation.

[0034] In the method for manufacturing a semiconductor device according to the present disclosure, a peeling step is performed in which the second substrate 12 is peeled off from the bonded substrate 10 that has been processed in the processing step.

[0035] Note that, during the peeling step, a process for reducing the bonding strength of bonding layer 19 may be performed. For example, if bonding layer 19 contains an ultraviolet-curable resin, second substrate 12 is made of a material that transmits ultraviolet light, and then ultraviolet light is irradiated from the second surface 18 side of second substrate 12. The ultraviolet light passes through second substrate 12 and is irradiated onto bonding layer 19, curing the ultraviolet-curable resin contained in bonding layer 19. As a result, the bonding strength of bonding layer 19 between first substrate 11 and second substrate 12 is weakened. However, because bonding layer 19 is in close contact with second substrate 12 in the state of bonded substrate 10, even if the bonding strength of bonding layer 19 is somewhat reduced, a large force may still be required to peel second substrate 12.

[0036] Furthermore, in the peeling step, as described in Patent Document 1, a laser beam may be focused on the bonding layer 19 to remove a portion of the bonding layer 19, thereby reducing the area of ​​adhesion with the second substrate 12, thereby making it easier to peel the second substrate 12. However, if the bonding layer 19 is thin, the laser beam may damage the first substrate 11. In particular, in recent years, the thickness of the bonding layer in bonded substrates has been reduced due to factors such as device miniaturization and improved substrate stability during processing, and laser processing of the bonding layer may not be suitable. Furthermore, in the case of a bonded substrate in which the first substrate 11 and the second substrate 12 are directly bonded without the bonding layer 19, the process of removing a portion of the bonding layer 19 cannot be performed in the peeling step.

[0037] The bonded substrate peeling method of the present disclosure differs from the above-described methods in that it focuses a laser beam inside second substrate 12 to form a modified portion in second substrate 12, thereby generating stress in a direction that causes second substrate 12 to separate from first substrate 11. Because the laser beam is focused on second substrate 12, it is possible to put second substrate 12 itself into a state that promotes peeling from first substrate 11 without being restricted by the thickness of bonding layer 19 or the method of fixing second substrate 12 to first substrate 11. Furthermore, because the laser beam is focused inside second substrate 12, there is an advantage that damage caused by the laser beam is less likely to extend to first substrate 11 compared to when the laser beam is focused on thin bonding layer 19. The bonded substrate peeling method of the present disclosure will be described in detail below.

[0038] 3 shows a laser processing device 30 used when forming a modified portion inside the second substrate 12. The laser processing device 30 includes a holding table 31 that holds the bonded substrate 10, and a laser irradiation unit 32 that irradiates the bonded substrate 10 on the holding table 31 with a laser beam L from above.

[0039] Each part of the laser processing apparatus 30 is controlled by a control unit 33. The control unit 33 has a processor that generates signals for controlling each part of the laser processing apparatus 30, and a storage unit that stores various information. The processor controls the operation of each part of the laser processing apparatus 30 by reading and executing programs stored in the storage unit. In the following description, unless a control entity in the laser processing apparatus 30 is specified, it is assumed that the control is performed by the control unit 33.

[0040] The holding table 31 has an upward-facing holding surface on which the bonded substrate 10 is placed. The holding surface of the holding table 31 is formed of a porous member 39 (see FIGS. 4, 5, etc.) that communicates with a suction source (not shown), and negative pressure can be applied to the holding surface by operating the suction source. The bonded substrate 10 is placed on the holding table 31 with the back surface 14 of the first substrate 11 facing the holding surface of the holding table 31, and is held by suction on the holding table 31.

[0041] The laser irradiation unit 32 focuses the laser beam L emitted by the laser oscillator 34 using a focusing optical system 35 and irradiates the laser beam L onto the bonded substrate 10 held on the holding table 31. The laser oscillator 34 oscillates a pulsed laser beam having a wavelength that is absorbed by the second substrate 12. As an example, the laser oscillator 34 oscillates an infrared laser.

[0042] The holding table 31 is provided with a horizontal movement mechanism 36 that moves the holding table 31 in horizontal directions (X-axis direction, Y-axis direction). The horizontal movement mechanism 36 is configured by, for example, a ball screw mechanism that moves the holding table 31 by rotating a ball screw with a motor, or an air cylinder mechanism that moves the holding table 31 by the pressure of air supplied from an air source.

[0043] The horizontal movement mechanism is not limited to the above configuration, and may be any mechanism that changes the relative positions of the bonded substrate 10 held by the holding table 31 and the laser irradiation unit 32 to horizontally change the irradiation position of the laser beam L from the laser irradiation unit 32 onto the bonded substrate 10. For example, the horizontal movement mechanism may be configured to move the holding table 31 in the X-axis direction and the laser irradiation unit 32 in the Y-axis direction. Alternatively, the horizontal movement mechanism may be configured to move the laser irradiation unit 32 in the X-axis and Y-axis directions without moving the holding table 31.

[0044] The laser irradiation unit 32 is provided with an elevation mechanism 37 that moves the laser irradiation unit 32 in the vertical direction (Z-axis direction). The elevation mechanism 37 is configured by, for example, a ball screw mechanism or an air cylinder mechanism. By changing the position of the laser irradiation unit 32 in the vertical direction by the elevation mechanism 37, the position of the focal point of the laser beam L focused by the focusing optical system 35 changes in the thickness direction of the bonded substrate 10.

[0045] The laser processing device 30 is equipped with an imaging unit 38 that can capture an image of the holding table 31 side from above. The control unit 33 uses the imaging unit 38 to capture an image of the bonded substrate 10 on the holding table 31, and adjusts the position of the laser irradiation unit 32 relative to the bonded substrate 10 based on the captured image, thereby controlling the laser beam L to be irradiated at a desired position on the bonded substrate 10.

[0046] The peeling process for peeling the second substrate 12 from the first substrate 11 includes a first process for forming a modified portion inside the second substrate 12 using a laser processing device 30, and a second process for peeling and removing the second substrate 12 with the modified portion formed thereon from the first substrate 11.

[0047] 4 and 5 show a first embodiment of the bonded substrate peeling method, and particularly show a first step of forming a modified region 21 inside the second substrate 12. With the bonded substrate 10 held by suction on the holding table 31, a laser beam L is irradiated from the laser irradiation unit 32 under the control of the control unit 33, and the laser beam L is focused inside the second substrate 12. A modified region 21 is formed by modifying the second substrate 12 at the portion inside the second substrate 12 where the laser beam L is focused. The modification of the modified region 21 means that the density, refractive index, mechanical strength, and other physical properties inside the second substrate 12 become different from those of the surrounding area due to the irradiation of the laser beam L. As a result of the modification, the modified region 21 becomes a region with reduced strength compared to the surrounding area.

[0048] When the modified region 21 is formed inside the second substrate 12, a crack 22 is formed from the modified region 21 in the thickness direction of the second substrate 12. The crack 22 tends to progress in the thickness direction of the second substrate 12 toward either the first surface 17 or the second surface 18, whichever is closer to the modified region 21.

[0049] The control unit 33 controls the lifting mechanism 37 to adjust the position of the focused spot of the laser beam L in the thickness direction of the second substrate 12, and focuses the laser beam L on the first substrate 11 side of the center C of the second substrate 12 in the thickness direction, as shown in Fig. 4. As a result, a modified region 21 is formed inside the second substrate 12 on the first substrate 11 side of the center C in the thickness direction, and cracks 22 are formed that extend mainly from the modified region 21 toward the first surface 17 side. Note that cracks may also form from the modified region 21 toward the second surface 18 opposite the first surface 17, but these cracks are generally smaller (shorter) than the cracks 22 on the first surface 17 side and are unlikely to be long enough to reach the second surface 18.

[0050] The control unit 33 operates the horizontal movement mechanism 36 to relatively change the positions of the bonded substrate 10 and the laser irradiation unit 32 in the horizontal direction, thereby focusing the laser beam L at multiple positions inside the second substrate 12 to form multiple modified regions 21. As a result, cracks 22 extending from each modified region 21 toward the first surface 17 are formed. When multiple cracks 22 extending toward the first surface 17 of the second substrate 12 are formed, the area of ​​the first surface 17 side becomes larger than that of the second surface 18 side due to the gaps created by each crack 22 (the first surface 17 side becomes expanded). As a result, a warping force is generated in the second substrate 12 so that the first surface 17 side becomes convex and the second surface 18 side becomes concave, i.e., stress is generated in a direction that moves the second substrate 12 away from the first substrate 11. This stress makes the second substrate 12 more likely to peel from the first substrate 11.

[0051] As shown in FIG. 5, by forming the modified portion 21 over the entire second substrate 12, stress in a direction away from the first substrate 11 can be generated over the entire second substrate 12.

[0052] When stress in a direction away from the first substrate 11 is generated in the second substrate 12, the condition for the position of the focal point of the laser beam L in the thickness direction of the second substrate 12 is, as described above, at least the position is closer to the first substrate 11 than the center C of the second substrate 12 in the thickness direction, i.e., the range (first range) from the first substrate 11 side (first surface 17) to ½ of the thickness in the thickness direction of the second substrate 12. The position of the focal point of the laser beam L in the thickness direction of the second substrate 12 is preferably the range (second range) from the first substrate 11 side (first surface 17) to ¼ of the thickness, more preferably the range (third range) from 1 / 16 to 3 / 16 of the thickness from the first substrate 11 side (first surface 17), and even more preferably the position (optimum position) at about ⅛ of the thickness from the first substrate 11 side (first surface 17). As an example, if first substrate 11 is a wafer with a thickness of 780 μm and first surface 17 is the reference position for thickness (position of 0 μm thickness), a distance from first surface 17 of 0 μm to 390 μm is the first range, a distance from first surface 17 of 0 μm to 195 μm is the second range, a distance from first surface 17 of 48.75 μm to 146.25 μm is the third range, and a distance of approximately 97.5 μm (approximately 100 μm) from first surface 17 is the optimal position. Experimental results showed that in terms of the extent of propagation of cracks 22 from modified portion 21 and the minimal thermal impact of irradiation of laser beam L on first substrate 11, good results were obtained by setting the position of the focal point of laser beam L in the order of the optimal position, the third range, the second range, and the first range.

[0053] Regarding the spot diameter of the focal point of the laser beam L, the smaller the spot diameter, the more easily cracks 22 propagate from the modified portion 21, thereby efficiently generating stress in the second substrate 12 in a direction away from the first substrate 11. Reducing the spot diameter of the laser beam L may increase damage to the second substrate 12. However, the second substrate 12 is removed after processing the first substrate 11, and high quality is not required for the second substrate 12 after use. Therefore, in the first step of the peeling process, it is preferable to reduce the spot diameter of the laser beam L as much as possible. As an example, it is preferable to set the spot diameter of the focal point of the laser beam L to a value of 1 μm to 2 μm or less. Furthermore, the laser oscillator 34 is preferably set to oscillate a pulsed laser beam with an average output of 0.5 W to 2.0 W, more preferably an average output of approximately 1.0 W.

[0054] 4 and 5, a plurality of modified regions 21 are formed at predetermined intervals in the X-axis direction. In the Y-axis direction, the modified regions 21 may be formed as long, continuous lines, or may be formed as spots at predetermined intervals, similar to the X-axis direction.

[0055] After the first step of forming the modified portion 21 on the second substrate 12 using the laser processing device 30 is completed, the suction holding of the bonded substrate 10 by the holding table 31 of the laser processing device 30 is released, and the bonded substrate 10 is carried out from the laser processing device 30. Then, the second step of peeling the second substrate 12 from the first substrate 11 is performed. The second step is performed by a peeling device (not shown).

[0056] In the peeling device, the first substrate 11 is fixed to a holding table, and the second surface 18 of the second substrate 12 is held by suction using a vacuum-suction type holding pad. When fixing the first substrate 11 to the holding table, the back surface 14 of the first substrate 11 may be attached to tape arranged inside an annular frame, and the annular frame may be fixed to the holding table. By moving the holding pad away from the holding table while the first substrate 11 is fixed to the holding table, the second substrate 12 moves with the holding pad, and the second substrate 12 is peeled from the first substrate 11 and the bonding layer 19 at the first surface 17. The first step previously performed generates stress in the second substrate 12 in a direction away from the first substrate 11, reducing the adhesion of the second substrate 12 to the first substrate 11 and the bonding layer 19. This makes it easier to peel the second substrate 12 from the first substrate 11 and the bonding layer 19, and the second substrate 12 can be reliably removed with little force. This makes it possible to prevent damage to first substrate 11 that has been thinned by grinding.

[0057] The configuration of the peeling device and the method for peeling off the second substrate 12 in the second step are not limited to those described above. For example, if the second substrate 12 is made of a flexible material, instead of uniformly lifting up the entire second substrate 12 with a holding pad or the like, the outer edge of the second substrate 12 may be grasped and partially lifted in a direction away from the holding table, and the second substrate 12 may be peeled off in a diametrical direction.

[0058] Furthermore, the second substrate 12 may be peeled off from the first substrate 11 (the second step of the peeling process) on the holding table 31 of the laser processing device 30 without transporting the bonded substrate 10 from the laser processing device 30 to the peeling device.

[0059] After the peeling step of peeling the second substrate 12 from the first substrate 11 is performed, the bonding layer 19 is removed from the first substrate 11 as necessary.

[0060] As described above, in the peeling step, by focusing the laser beam L inside the second substrate 12 to form the modified portion 21, stress is generated in the direction in which the second substrate 12 moves away from the first substrate 11, making it easier to peel the second substrate 12 from the first substrate 11. Because the portion where the laser beam L is focused is inside the second substrate 12, there is no need to focus the laser beam L on the bonding layer 19, and even if the bonding layer 19 is thin, damage to the first substrate 11 by the laser beam L can be prevented.

[0061] Furthermore, because the target on which the modified portion 21 is formed is the second substrate 12, the method is also applicable to a type of bonded substrate in which the first substrate 11 and the second substrate 12 are directly bonded without the bonding layer 19, unlike the bonded substrate 10 having the illustrated configuration. In other words, the method for peeling off a bonded substrate in this embodiment is not restricted by the means for bonding the first substrate 11 and the second substrate 12, and is highly versatile and can be applied to bonded substrates of various types.

[0062] As described above, in the case of a bonded substrate in which one or both of device surface 13 of first substrate 11 and first surface 17 of second substrate 12 are subjected to a hydrophilic treatment and bonded together by hydrogen bonding, bubbles are generated at the bonding interface between first substrate 11 and second substrate 12 by heating the substrate to a second temperature higher than the first temperature at which adhesion is improved. However, even if bubbles are generated at the bonding interface between first substrate 11 and second substrate 12, if second substrate 12 cannot be easily peeled from first substrate 11, the method for peeling bonded substrates according to this embodiment can be applied to generate stress in a direction that separates second substrate 12 from first substrate 11, thereby making peeling easier.

[0063] In the peeling process, if modified portions 21 and cracks 22 that generate stress in a direction away from first substrate 11 are formed all over second substrate 12, second substrate 12 may become significantly warped. In particular, if second substrate 12 becomes convex downward due to cracks 22 that expand the first surface 17 side, the amount of warping of second substrate 12 is likely to increase at the outer edge of bonded substrate 10. In this case, it is necessary to consider the possibility that the warped outer edge of second substrate 12 may interfere with surrounding structures.

[0064] Furthermore, if, after forming modified portion 21 on second substrate 12 in laser processing apparatus 30, second substrate 12 is not immediately peeled from first substrate 11, but rather bonded substrate 10 is transported while maintaining first substrate 11 and second substrate 12 bonded together, excessive warpage of second substrate 12 may interfere with transport of bonded substrate 10. For example, when bonding substrate 10 is transported using a holding pad that suction-holds second surface 18 of second substrate 12 from above, if second substrate 12 has a significantly warped shape, it becomes difficult for the holding pad to stably hold second substrate 12. Alternatively, a transport device with a special structure capable of holding second substrate 12 with a significantly warped shape is required.

[0065] Therefore, in the peeling process, it is necessary to appropriately control the degree of warpage of second substrate 12. To address this requirement, in a second embodiment of the bonded substrate peeling method shown in Fig. 6, modified portions are formed at different positions in the thickness direction of second substrate 12, so that the direction of warpage of second substrate 12 changes partially, thereby preventing second substrate 12 from warping significantly in the same direction. The details will be described below.

[0066] 6, the second substrate 12 is divided into a first region Ea and a second region Eb in a direction intersecting the first surface 17, which is the surface facing the first substrate 11. Then, in each of the first region Ea and the second region Eb, a laser beam L is focused as follows based on the control of the control unit 33 to form a modified portion.

[0067] In the first region Ea, similar to the first embodiment (FIGS. 4 and 5), a laser beam L is focused to form a modified region 21 inside the second substrate 12 on the first substrate 11 side (i.e., the side closer to the first surface 17) than the center of the second substrate 12 in the thickness direction. A plurality of modified regions 21 are formed at predetermined intervals in the X-axis direction, and cracks 22 are formed from each modified region 21 toward the first surface 17 of the second substrate 12. As a result, in the first region Ea, the area on the first surface 17 side is larger than that on the second surface 18 side due to gaps created by the cracks 22, and a warp occurs in the second substrate 12 in which the first surface 17 side is convex and the second surface 18 side is concave.

[0068] In the second region Eb, the laser beam L is focused inside the second substrate 12 on the side opposite to the first substrate 11 from the center of the second substrate 12 in the thickness direction (i.e., the side closer to the second surface 18) to form modified regions 23. A plurality of modified regions 23 are formed at predetermined intervals in the X-axis direction. Cracks 24 extending mainly toward the second surface 18 side are formed from each modified region 23 formed at a position closer to the second surface 18 in the thickness direction of the second substrate 12. As a result, in the second region Eb, the area on the second surface 18 side is larger than that on the first surface 17 side due to the gaps created by the cracks 24, and warping occurs in the second substrate 12 with a convex shape on the second surface 18 side and a concave shape on the first surface 17 side.

[0069] In this way, by reversing the direction of warping of second substrate 12 in first region Ea and second region Eb and giving second substrate 12 a corrugated cross-sectional shape, the amount of warping of second substrate 12 relative to first substrate 11 can be reduced compared to a shape in which the entire second substrate 12 warps in the same direction. Therefore, while achieving the effect of facilitating peeling of second substrate 12 due to stress in the direction in which second substrate 12 moves away from first substrate 11, it is possible to prevent second substrate 12 from warping excessively large before peeling. This prevents problems such as a significantly warped second substrate 12 interfering with other structures or making it difficult to hold second substrate 12 on a transfer pad or the like when transferring bonded substrate 10.

[0070] 7 and 8 are plan views of the bonded substrate 10 viewed from the second surface 18 side of the second substrate 12, and show examples of the arrangement of the first region Ea and the second region Eb in a direction parallel to the surface (first surface 17 and second surface 18) of the second substrate 12.

[0071] 7, the first regions Ea and the second regions Eb each extend in a first direction (Y-axis direction) parallel to the surface of the second substrate 12, and each region Ea, Eb crosses the second substrate 12 in the first direction (Y-axis direction). Furthermore, the first regions Ea and the second regions Eb are alternately arranged along a second direction (X-axis direction) parallel to the surface of the second substrate 12 and intersecting the first direction.

[0072] In the arrangement example shown in Figure 8, the first regions Ea and second regions Eb are arranged in a checkerboard pattern, alternating in both a first direction (Y-axis direction) and a second direction (X-axis direction) parallel to the surface of the second substrate 12.

[0073] As in these arrangement examples, by alternately configuring the first regions Ea and the second regions Eb in the second substrate 12, it is possible to reliably obtain the effect of making it easier to peel the second substrate 12 from the first substrate 11 while suppressing excessive warping of the second substrate 12.

[0074] 7 and 8, the boundary between the first region Ea and the second region Eb is linear, but the boundary between the first region Ea and the second region Eb does not have to be linear. Also, in the arrangement examples of Fig. 7 and 8, the areas of the first region Ea and the second region Eb are roughly equal, but the ratio of the areas of the first region Ea and the second region Eb may be different.

[0075] 9, the position of the first region Ea in the second substrate 12 is preferably set to correspond to the remaining portion of the singulated first substrate 11. That is, in the portion of the first substrate 11 corresponding to the device region where the devices 16 are formed, the second substrate 12 is set to the first region Ea, and in the portion other than the device region (such as the planned division lines 15), the second substrate 12 is set to the second region Eb. By setting them in this manner, the apex of the convex shape on the first surface 17 of the second substrate 12 contacts the center of each singulated device region of the first substrate 11, which makes it easier to peel the second substrate 12 from the device region after singulation.

[0076] In the second embodiment described above, a region (first region Ea) for forming the modified region 21 located on the first substrate 11 side (first surface 17 side) in the thickness direction of the second substrate 12, and a region (second region Eb) for forming the modified region 23 located on the opposite side of the thickness direction of the second substrate 12 from the first substrate 11 (second surface 18 side) are partitioned and arranged in a direction parallel to the surface of the second substrate 12. That is, either the modified region 21 or the modified region 23 is formed in each region set in the second substrate 12. As a method for correcting warpage of the second substrate 12 without partitioning the regions in this way, it is also possible to form a modified region as in the third embodiment of the bonded substrate peeling method shown in FIG. 10.

[0077] 10 , in the third embodiment, similar to the first embodiment described above, modified regions 21 (including cracks 22 extending toward the first surface 17) are formed at predetermined intervals throughout the second substrate 12, on the side of the second substrate 12 facing the first substrate 11 from the center of the second substrate 12 in the thickness direction, thereby warping the second substrate 12 so that the first surface 17 side is convex. Subsequently, modified regions 23 (including cracks 24 extending toward the second surface 18) are formed at predetermined intervals throughout the second substrate 12, on the side of the second substrate 12 facing away from the first substrate 11 from the center of the second substrate 12 in the thickness direction, thereby correcting (alleviating) the warpage of the second substrate 12. In a direction parallel to the surface of the second substrate 12, the modified regions 21 and 23 are not separated into regions where the modified regions 21 and 23 are formed, and the modified regions 21 and 23 are arranged side by side in the thickness direction of the second substrate 12.

[0078] The formation of the modified portion 23 has the effect of warping the second substrate 12 so that the second surface 18 side becomes convex, and therefore, by forming the modified portion 23 over the entire second substrate 12, the warping of the second substrate 12 caused by the formation of the modified portion 21 is offset. By correcting the warping of the second substrate 12 in this manner, the second surface 18 of the second substrate 12 can be reliably adsorbed and held by a transport pad or the like, making it possible to easily transport the bonded substrate 10.

[0079] 10, the arrangement density of the modified regions 21 in the X-axis direction and the arrangement density of the modified regions 23 in the X-axis direction are set to be approximately the same, but it is also possible to make the arrangement density of the modified regions 21 different from the arrangement density of the modified regions 23. As an example, the arrangement density of the modified regions 21 may be set higher than that of the modified regions 23.

[0080] In the second embodiment described above, the modified regions 21 are formed in the first region Ea and the modified regions 23 are formed in the second region Eb. However, as a modified example, it is also possible to form the modified regions 21 in the first region Ea while forming neither the modified regions 21 nor the modified regions 23 in the second region Eb. That is, modified region groups including a plurality of modified regions 21 may be arranged intermittently at predetermined intervals in a direction parallel to the surface of the second substrate 12. By configuring the modified region groups to be arranged intermittently as in this modified example, the increase in the area on the first surface 17 side is reduced compared to when a large number of modified regions 21 are formed densely over the entire second substrate 12, thereby achieving the effect of suppressing warping of the second substrate 12.

[0081] Although not shown, the positions at which the modified regions 21 are formed may differ from one another in the thickness direction of the second substrate 12. When the modified regions 21 are formed in positions close to the first surface 17, the distance from the modified regions 21 to the first surface 17 is short, and the maximum length of the cracks 22 extending from the modified regions 21 toward the first surface 17 is short. As a result, the degree of area increase on the first surface 17 side due to the cracks 22 is low, and warping of the second substrate 12 is likely to be small. Conversely, when the modified regions 21 are formed in positions far from the first surface 17 but not beyond the center of the thickness direction of the second substrate 12, the distance from the modified regions 21 to the first surface 17 is long, and the maximum length of the cracks 22 extending from the modified regions 21 toward the first surface 17 is long. As a result, the degree of area increase on the first surface 17 side due to the cracks 22 is high, and warping of the second substrate 12 is likely to be large.

[0082] Therefore, by intentionally making the positions at which the modified portions 21 are formed unevenly in the thickness direction of the second substrate 12, rather than making the positions at which the individual modified portions 21 are formed uniformly in the thickness direction of the second substrate 12, it is possible to control the degree of warpage of the second substrate 12. For example, in a specific portion (such as the outer edge portion) of the second substrate 12, by forming the modified portions 21 at a position close to the first surface 17 and shortening the cracks 22, it is possible to reduce the warpage of the second substrate 12 in that specific portion.

[0083] The embodiments of the present invention are not limited to the above-described embodiments and modifications, and may be variously changed, substituted, or modified without departing from the spirit of the technical idea of ​​the present invention. Furthermore, if the technical idea of ​​the present invention can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea of ​​the present invention. [Industrial Applicability]

[0084] As described above, according to the present disclosure, it is possible to easily peel off the second substrate in the bonded substrate while preventing damage to the first substrate, thereby achieving improved quality and productivity of semiconductor devices and the like that use the bonded substrate in the manufacturing process. [Explanation of symbols]

[0085] 10: Bonded substrate 11: First board 12: Second substrate (support substrate) 13: Device surface 14: Back side 15: Planned division line 16: Devices (semiconductor devices) 17: 1st page 18:Second side 19: Bonding layer 20: Machining groove 21: Modification section 22: Crack 23: Modification section 24: Crack 30: Laser processing equipment 31: Holding table 32: Laser irradiation unit 33: Control unit 34: Laser oscillator 35: Condensing optical system 36: Horizontal movement mechanism 37: Lifting mechanism 38: Imaging unit 39: Porous materials C: Center of the second substrate in the thickness direction Ea: 1st area Eb: 2nd area L: Laser beam

Claims

1. A method for peeling a second substrate from a bonded substrate formed by bonding a first substrate and a second substrate supporting the first substrate, the method comprising: a laser beam is focused inside the second substrate to form a modified portion in the second substrate, thereby generating stress in a direction in which the second substrate moves away from the first substrate; A method for peeling bonded substrates, comprising:

2. The laser beam is focused on the first substrate side from the center of the second substrate in the thickness direction.

2. The method for peeling bonded substrates according to claim 1, wherein the bonding step comprises:

3. the second substrate includes a first region and a second region separated in a direction intersecting a surface of the second substrate facing the first substrate, In the first region, the laser beam is focused inside the second substrate on the first substrate side from the center of the second substrate in the thickness direction; In the second region, the laser beam is focused inside the second substrate on a side opposite to the first substrate from the center of the second substrate in the thickness direction.

2. The method for peeling bonded substrates according to claim 1, wherein the bonding step comprises:

4. The first region and the second region are extending in a first direction parallel to a surface of the second substrate; the first and second substrates are arranged alternately along a second direction parallel to the surface of the second substrate and intersecting the first direction; 4. The method for peeling bonded substrates according to claim 3, wherein the bonding step comprises:

5. the first substrate has a device surface on which devices are formed; the second substrate is a support substrate; the device surface is bonded to the support substrate in a facing manner; 5. The method for peeling a bonded substrate according to claim 1, wherein the bonding substrate is peeled off.

6. a processing step of processing the first substrate of a bonded substrate formed by bonding a first substrate and a second substrate supporting the first substrate; a peeling step of peeling the second substrate from the bonded substrate processed in the processing step, In the peeling step, a laser beam is focused inside the second substrate to form a modified portion in the second substrate, thereby generating stress in a direction in which the second substrate separates from the first substrate.

1. A method for manufacturing a semiconductor device.

7. The processing step includes a singulation step of singulating the first substrate.

7. The method for manufacturing a semiconductor device according to claim 6.

8. The peeling step includes concentrating a laser beam on a side of the second substrate toward the first substrate from a center of the second substrate in a thickness direction.

8. The method for manufacturing a semiconductor device according to claim 6 or 7.

9. the second substrate includes a first region and a second region separated in a direction intersecting a surface of the second substrate; The peeling step includes: In the first region, the laser beam is focused inside the second substrate on the first substrate side from the center of the second substrate in the thickness direction; In the second region, the laser beam is focused inside the second substrate on a side opposite to the first substrate from the center of the second substrate in the thickness direction.

8. The method for manufacturing a semiconductor device according to claim 6 or 7.

10. The first region and the second region are extending in a first direction parallel to a surface of the second substrate; the first and second substrates are arranged alternately along a second direction parallel to the surface of the second substrate and intersecting the first direction; 10. The method for manufacturing a semiconductor device according to claim 9.

11. the first substrate has a device surface on which devices are formed; the second substrate is a support substrate; the device surface is bonded to the support substrate in a facing manner; 8. The method for manufacturing a semiconductor device according to claim 6 or 7.

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