Fabrication methods for single-crystal silicon wafers

Abstract

[Problem] A method for processing a single-crystal silicon wafer is provided, which can shorten the processing time when the wafer is separated by using the release layer formed inside the wafer as the separation starting point, and reduce the probability of component damage. [Solution] For a single-crystal silicon wafer manufactured in such a way that a specific crystal plane (e.g., crystal plane (100)) contained in the crystal plane {100} is exposed on the front and back sides respectively, a laser beam is irradiated along a first direction parallel to the specific crystal plane and with an angle of less than 5° relative to the specific crystal direction (e.g., crystal direction [010]) contained in the crystal direction <100>, thereby forming a release layer, which becomes the separation starting point between the front and back sides of the single-crystal silicon wafer.

Description

Technical Field

[0001] This invention relates to a processing method for monocrystalline silicon wafers, wherein after forming a release layer inside the monocrystalline silicon wafer, the release layer is used as the starting point for separation to separate the monocrystalline silicon wafer. Prior Technology

[0002] Semiconductor device (hereinafter referred to as "device") chips are generally manufactured using disk-shaped single-crystal silicon wafers (hereinafter referred to as "wafers"). Specifically, this wafer is divided into multiple regions by pre-defined dicing lines arranged in a grid pattern, and devices are formed on the front side of each region. Then, the wafer is diced along the pre-defined dicing lines to manufacture the chip.

[0003] Furthermore, sometimes through-silicon vias (TSVs) are incorporated into wafers for purposes such as high integration of packages containing multiple chips. In this package, for example, electrodes contained in different chips can be electrically connected through the TSVs.

[0004] The TSV (Transfer Vessel) is disposed on the wafer in the following order: First, a groove is formed on the front side of the wafer. Next, the TSV is disposed in this groove. Next, the front side of the wafer is attached to a support wafer. Next, the back side of the wafer is ground until the TSV is exposed on the back side of the wafer.

[0005] Therefore, in wafers, the outer periphery is often chamfered to prevent cracking. Furthermore, if the back side of a wafer with a chamfered outer periphery is ground until the wafer thickness is less than half, the back side of this outer periphery will become a blade-like shape.

[0006] In this situation, during wafer grinding, stress will concentrate on the back side of the outer peripheral region, making the wafer more prone to breakage and raising concerns about a decrease in the yield of the wafer obtained from the wafer. Therefore, it has been proposed to remove a portion of the front side of the outer peripheral region (so-called trimming) before grinding the back side of such wafers (for example, see Patent Document 1).

[0007] In this way, at the point when the remaining portion of the back side of the peripheral region is removed by grinding, the side surface of the wafer becomes approximately perpendicular to the front and back sides. Therefore, no stress concentration occurs on the back side of the peripheral region during wafer grinding, making the wafer less prone to breakage. As a result, wafer yield degradation can be suppressed.

[0008] However, after trimming, when the back side of the wafer is ground until the TSV is exposed on the back side, the amount of material removed from the wafer increases, and the amount of wear on the grinding stone required to grind this wafer increases. In this case, the cost of the chips or packages manufactured using this wafer increases, and there are concerns about the long-term processing time.

[0009] In view of this, a method has been proposed in which a spot formed by irradiating a wafer is positioned inside the wafer and has a laser beam with a wavelength that can penetrate the wafer, thereby forming a release layer inside the wafer, and then using this release layer as a separation starting point to separate the wafer (for example, see Patent Document 2).

[0010] In this method, firstly, a laser beam is irradiated onto a first annular region of the wafer that will not diffuse when irradiated with the laser beam (specifically, an annular region further inward than the chamfered outer peripheral region). This forms a release layer (a cylindrical release layer), which becomes the starting point for separation between the area where the components are formed and the outer peripheral region of the wafer.

[0011] Next, the laser beam is irradiated into a second region of the wafer that will not produce diffusion when irradiated with the laser beam (specifically, a circular region further inward than the chamfered outer perimeter region). This forms a release layer (a disk-shaped release layer), which becomes the starting point for separation between the front and back sides of the wafer.

[0012] Next, by applying external force to the wafer, the wafer is separated from the cylindrical and disk-shaped release layers. That is, the peripheral region is separated from the area where the components are formed on the wafer, and the back side is separated from the front side of the wafer.

[0013] This wafer separation reduces the amount of wafer grinding required until the TSV is exposed on the back side of the wafer, thus reducing the wear of the grinding stone needed to grind the wafer. As a result, it can suppress the increase in cost of chips or packages manufactured using this wafer, and also shorten the time required to grind the wafer. [Known Technical Literature] [Patent Literature]

[0014] [Patent Document 1] Japanese Patent Application Publication No. 2007-158239 [Patent Document 2] Japanese Patent Application Publication No. 2020-136442 Summary of the Invention

[0015] [The problem that the invention aims to solve] The aforementioned peeling layer consists of modified regions and cracks. The modified regions are formed by the disordered crystal structure of the single-crystal silicon constituting the wafer, and the cracks extend from these modified regions. Specifically, when the aforementioned laser beam is irradiated onto the wafer, modified regions are formed inside the wafer centered on the focal point of the laser beam. Furthermore, cracks extend from these modified regions along predetermined crystal planes of the single-crystal silicon constituting the wafer.

[0016] Therefore, single-crystal silicon is generally most prone to cracking in a specific crystal plane contained in crystal plane {111}. For example, in a wafer manufactured in a manner that exposes a specific crystal plane contained in crystal plane {100} (e.g., crystal plane (100)) on the front and back sides respectively, along the crystal direction <110> When a laser beam is irradiated with a specific crystal direction that is parallel to that specific crystal plane (e.g., crystal direction

[0011] ), a large number of cracks will be generated extending from the modified region along the specific crystal plane (e.g., crystal plane (111)) contained in the crystal plane {111}.

[0017] Then, the acute angle formed by a specific crystal plane (e.g., crystal plane (100)) contained in the crystal plane {100} of the single crystal silicon and a specific crystal plane (e.g., crystal plane (111)) contained in the crystal plane {111} is about 54.7°. Therefore, when a laser beam is irradiated onto the wafer as described above, a large number of cracks will be generated extending from the modified region in a direction inclined at about 54.7° relative to the front or back side of the wafer.

[0018] That is, if the direction of this crack extension is decomposed into a component parallel to the front and back sides of the wafer (parallel component) and a component perpendicular to the front and back sides of the wafer (vertical component), the vertical component is greater than the parallel component. Therefore, in the case where a release layer (disc-shaped release layer) is formed by irradiating the wafer with a laser beam as described above, which serves as the separation starting point between the front and back sides of the wafer, there are concerns about the following problems.

[0019] First, in this case, because the parallel component of the direction of crack extension is small, the interval between adjacent modified regions needs to be narrowed in order to connect the modified regions that are separated by cracks. Then, in the case of narrowing the interval between adjacent modified regions, the processing time (laser beam irradiation time) required to form the disc-shaped peeling layer needs to be extended.

[0020] Furthermore, in this case, because the vertical component of the crack extension direction is larger, there is a concern that the crack may extend from the disc-shaped release layer toward the front side of the wafer, potentially damaging the device. In addition, although the probability of device damage can be reduced by forming a disc-shaped release layer at a position sufficiently away from the front side of the wafer, this would lead to an increase in the amount of material removed during subsequent wafer grinding.

[0021] In view of the above problems, the purpose of this invention is to provide a processing method for single-crystal silicon wafers, which can shorten the processing time when the wafer is separated by using the release layer formed inside the wafer as the separation starting point, and reduce the probability of component damage.

[0022] [Technical means to solve the problem] According to the present invention, a method for processing a single-crystal silicon wafer is provided. For a single-crystal silicon wafer manufactured in a manner that exposes specific crystal faces {100} on both the front and back sides, and having multiple elements formed on the front side and a chamfered outer periphery, a laser beam with a wavelength capable of penetrating single-crystal silicon is irradiated, forming a release layer inside the single-crystal silicon wafer. This release layer is then used as a separation starting point to separate the single-crystal silicon wafer. The method for processing the single-crystal silicon wafer includes: a bonding step in which the front side of the single-crystal silicon wafer is bonded to the front side of a supporting wafer; and a first release layer forming step in which the laser beam is irradiated from the back side of the single-crystal silicon wafer onto a first annular region of the single-crystal silicon wafer that is further inward than the outer periphery to form a first release layer, the first release layer becoming part of the single-crystal silicon wafer. The silicon wafer formation includes a separation starting point between the region of the plurality of components and the outer peripheral region; a second release layer formation step, in which a laser beam is irradiated from the back side of the single-crystal silicon wafer into a second region further inward than the outer peripheral region, thereby forming a second release layer, which becomes the separation starting point between the front side and the back side of the single-crystal silicon wafer; and a separation step, in which, after performing the bonding step, the first release layer formation step, and the second release layer formation step, external force is applied to the single-crystal silicon wafer to separate the single-crystal silicon wafer using the first release layer and the second release layer as separation starting points, wherein, in the second release layer formation step, the second release layer is formed by repeatedly performing the laser beam irradiation step and the indexing feed step, wherein the laser beam irradiation step is performed along a direction parallel to the specific crystal plane and relative to the crystal direction. <100> The single-crystal silicon wafer is moved relative to the focal point by a first direction in which the angle formed by the specific crystal orientation is less than 5°, while the laser beam is irradiated on the linear region along the first direction in the second region. The indexing feed step is carried out along a second direction that is parallel to the specific crystal plane and orthogonal to the first direction, thereby moving the internal position of the single-crystal silicon wafer that forms the focal point by irradiating the laser beam.

[0023] Furthermore, it is preferable to perform the first release layer formation step before performing the second release layer formation step.

[0024] Furthermore, it is preferable that the second region is located further inside the first region.

[0025] Furthermore, it is preferable that the first release layer is formed in the first release layer formation step in a manner that does not reach the back side of the single-crystal silicon wafer.

[0026] Furthermore, preferably, in the first release layer formation step, the laser beam is irradiated in such a way that the formed focal point is closer to the outer peripheral region and thus closer to the front side of the single-crystal silicon wafer, thereby forming the first release layer as if along the side of a frustum, wherein the first bottom surface of the frustum is located on the front side of the single-crystal silicon wafer, and the second bottom surface, which has a diameter shorter than the first bottom surface, is located inside the single-crystal silicon wafer.

[0027] [Invention Benefits] In this invention, for a single-crystal silicon wafer manufactured in a manner that exposes a specific crystal plane (e.g., crystal plane (100)) contained in the crystal plane {100} on the front and back sides respectively, along a direction parallel to the specific crystal plane and relative to the crystal direction... <100> A laser beam is irradiated in a first direction where the angle formed by the specific crystal orientation (e.g., crystal orientation

[0010] ) is less than 5°, thereby forming a release layer (second release layer), which becomes the starting point for separation between the front side and the back side of the single crystal silicon wafer.

[0028] In this case, among the cracks extending from the modified region, the cracks along the specific crystal planes contained in the crystal plane {n10} (n is a natural number less than 10) (e.g., crystal plane (101)) become more numerous than the cracks along the specific crystal planes contained in the crystal plane {111} (e.g., crystal plane (111)). Moreover, the acute angle formed by the specific crystal planes contained in the crystal plane {100} and the specific crystal planes contained in the crystal plane {n10} is 45° or less.

[0029] Therefore, in this invention, compared to a single-crystal silicon wafer manufactured by means of exposing a specific crystal plane contained in crystal plane {100} on the front and back sides respectively, along the crystal direction parallel to that specific crystal plane... <110> When a second peeling layer is formed by irradiating a laser beam with a specific crystal orientation (e.g., crystal orientation

[0011] ), the component of the direction of crack extension that is parallel to the front and back sides of the wafer (parallel component) becomes larger, and the component perpendicular to the wafer (vertical component) becomes smaller.

[0030] Therefore, in this invention, because the parallel component of the crack propagation direction is increased, the interval between adjacent modified regions can be lengthened. As a result, the travel distance (indexing) in the indexing feed step can be lengthened, and the processing time (laser beam irradiation time) required to form the release layer that becomes the separation starting point between the front and back sides of the wafer can be shortened.

[0031] Furthermore, in this invention, because the vertical component of the crack propagation direction is reduced, the crack is less likely to extend from this release layer toward the front side of the wafer. As a result, the probability of device damage can be reduced when separating the front and back sides of the wafer. Simple Explanation of the Diagram

[0032] Figure 1(A) is a schematic top view of an example of a wafer, and Figure 1(B) is a schematic cross-sectional view of an example of a wafer. Figure 2 is a flowchart illustrating an example of a wafer fabrication method. Figure 3 is a schematic cross-sectional view showing the front side of the wafer being attached to the front side of the supporting wafer. Figure 4 is a perspective view schematically showing an example of a laser processing apparatus. Figure 5 is a schematic diagram showing the travel of the laser beam in a laser beam irradiation unit. Figure 6 is a schematic partial cross-sectional side view showing the situation of irradiating a rotating wafer with a laser beam. Figure 7 is a flowchart schematically illustrating an example of the second peeling layer formation step. Figure 8 is a schematic partial cross-sectional side view of a wafer moving along the X-axis being irradiated with a laser beam. Figure 9 is a schematic cross-sectional view of adjacent exfoliation layers formed inside the crystal rod. Figures 10(A) and 10(B) are schematic partial cross-sectional side views illustrating the separation of wafers. Figure 11 is a schematic partial cross-sectional side view showing the situation of irradiating a rotating wafer with a laser beam. Figure 12 is a diagram showing the width of the release layer formed inside the wafer when a laser beam is irradiated onto a straight area along different crystal directions. Figure 13 is a top view schematically showing an example of a wafer variation. Figures 14(A) and 14(B) are schematic partial cross-sectional side views illustrating the separation of the area where multiple components are formed on a wafer from the peripheral area. Figures 15(A) and 15(B) are schematic partial cross-sectional side views showing the separation of the front and back sides of a wafer. Implementation

[0033] Referring to the accompanying drawings, embodiments of the present invention will be described. FIG1(A) is a schematic top view showing an example of a wafer (single-crystal silicon wafer), and FIG1(B) is a schematic cross-sectional view showing an example of a wafer (single-crystal silicon wafer). Furthermore, the crystal orientation of the single-crystal silicon constituting this wafer is also shown in FIG1(A).

[0034] The wafer 11 shown in Figures 1(A) and 1(B) is composed of cylindrical single-crystal silicon with specific crystal planes (here, for convenience, crystal plane (100)) exposed in the front side 11a and back side 11b respectively. That is, this wafer 11 is composed of cylindrical single-crystal silicon with vertical lines (crystal axes) of the front side 11a and back side 11b along the crystal direction

[0100] .

[0035] Furthermore, although wafer 11 is manufactured in a manner that exposes the crystal plane (100) on the front side 11a and the back side 11b respectively, due to manufacturing errors, its front side 11a and back side 11b may also be surfaces that are slightly inclined from the crystal plane (100). Specifically, the front side 11a and back side 11b of wafer 11 may also be surfaces whose acute angle with the crystal plane (100) is less than 1°.

[0036] That is, the crystal axis of wafer 11 can also be along a direction whose acute angle with the crystal direction

[0100] is less than 1°. Furthermore, a notch 13 is formed on the side surface 11c of wafer 11, and when viewed through this notch 13, the center of wafer 11 is located in the crystal direction. <110> The specific crystal plane contained therein (here, for convenience, it is set as the crystal orientation

[0011] ).

[0037] Furthermore, the wafer 11 is divided into multiple regions by multiple intersecting slitting lines, and on the front side 11a of each region, components 15 such as IC (Integrated Circuit), LSI (Large Scale Integration), semiconductor memory, or CMOS (Complementary Metal Oxide Semiconductor) image sensors are formed.

[0038] Furthermore, a groove for setting TSVs can also be formed on the front side 11a of wafer 11. Also, the outer periphery of wafer 11 is chamfered. That is, the side side 11c of wafer 11 is curved in a way that protrudes outwards. In addition, no components 15 are formed in the outer periphery of wafer 11. That is, the area of ​​wafer 11 where multiple components 15 are formed is surrounded by its outer periphery.

[0039] Figure 2 is a flowchart schematically illustrating an example of a wafer fabrication method. Specifically, in this method, a laser beam with a wavelength that can penetrate the wafer 11 is irradiated onto the wafer 11 by positioning a concentrated spot inside the wafer 11, thereby forming a release layer inside the wafer 11. The wafer 11 is then separated from the wafer 11 by using this release layer as the starting point for separation.

[0040] Specifically, in this method, firstly, the front side 11a of wafer 11 is bonded to the front side 17a of support wafer 17 (bonding step: S1). Figure 3 is a schematic cross-sectional view showing the case where the front side 11a of wafer 11 is bonded to the front side 17a of support wafer 17. Furthermore, the support wafer 17 that can be bonded to wafer 11 has, for example, the same shape as wafer 11.

[0041] This support wafer 17, like the wafer 11, can be made of monocrystalline silicon, and multiple components can be formed on its front side 17a. Furthermore, an adhesive 19, such as an acrylic adhesive or an epoxy adhesive, is provided on the front side 17a of the support wafer 17.

[0042] Then, in the bonding step (S1), with the back side 17b of the supporting wafer 17 already supported, the front side 11a of the wafer 11 is pressed onto the front side 17a of the supporting wafer 17 using the adhesive 19. This forms a bonded wafer, where the front side 11a of the wafer 11 is bonded to the front side 17a of the supporting wafer 17.

[0043] Next, a release layer is formed inside the wafer 11 using a laser processing apparatus. Figure 4 is a perspective view schematically showing an example of a laser processing apparatus used to form a release layer inside the wafer 11. Furthermore, the X-axis direction (left-right direction) and Y-axis direction (front-back direction) shown in Figure 4 are mutually orthogonal directions on the horizontal plane, and the Z-axis direction (up-down direction) is a direction orthogonal to both the X-axis and Y-axis directions (vertical direction).

[0044] The laser processing apparatus 2 shown in Figure 4 has a base 4 that supports all its components. A horizontal moving mechanism 6 is disposed on the upper surface of this base 4. Furthermore, the horizontal moving mechanism 6 has a pair of Y-axis guide rails 8 that are fixed to the upper surface of the base 4 and extend along the Y-axis direction.

[0045] The Y-axis moving plate 10 is connected to the upper surface of the pair of Y-axis guide rails 8 in a manner that allows it to slide along the pair of Y-axis guide rails 8. Furthermore, a screw 12 extending along the Y-axis direction is disposed between the pair of Y-axis guide rails 8. A motor 14 for rotating the screw 12 is connected to the front end (one end) of the screw 12.

[0046] Furthermore, a nut portion (not shown) is provided on the surface of the screw shaft 12 with a helical groove to form a ball screw. The nut portion accommodates multiple balls, which roll on the surface of the rotating screw shaft 12. That is, if the screw shaft 12 rotates, the multiple balls will circulate within the nut portion, and the nut portion will move along the Y-axis direction.

[0047] Furthermore, this nut is fixed to the lower surface of the Y-axis moving plate 10. Therefore, if the screw 12 is rotated by the motor 14, the Y-axis moving plate 10 and the nut move together along the Y-axis direction. In addition, a pair of X-axis guide rails 16 extending along the X-axis direction are fixed to the upper surface of the Y-axis moving plate 10.

[0048] The X-axis moving plate 18 is connected to the upper surface of the pair of X-axis guide rails 16 in a manner that allows it to slide along the pair of X-axis guide rails 16. Furthermore, a screw 20 extending along the X-axis direction is disposed between the pair of X-axis guide rails 16. A motor 22 for rotating the screw 20 is connected to one end of this screw 20.

[0049] Furthermore, a nut portion (not shown) is provided on the surface of the screw shaft 20 with a helical groove to form a ball screw. The nut portion accommodates multiple balls, which roll on the surface of the rotating screw shaft 20. That is, if the screw shaft 20 rotates, the multiple balls will circulate within the nut portion, and the nut portion will move along the X-axis direction.

[0050] Furthermore, this nut is fixed to the lower surface of the X-axis moving plate 18. Therefore, if the screw shaft 20 is rotated by the motor 22, the X-axis moving plate 18 and the nut move together along the X-axis direction.

[0051] A cylindrical stage base 24 is disposed on the upper surface of the X-axis moving plate 18. A holding stage 26 for holding the aforementioned bonded wafer is disposed on the upper part of the stage base 24. This holding stage 26 has, for example, a circular upper surface (holding surface) that is parallel to the X-axis and Y-axis directions, and a perforated plate 26a is exposed in this holding surface.

[0052] Furthermore, a rotary drive source (not shown) such as a motor is connected to the lower part of the worktable base 24. When this rotary drive source is activated, the holding table 26 rotates through the center of the holding surface, using a straight line parallel to the Z-axis as its axis of rotation. Furthermore, when the aforementioned horizontal movement mechanism 6 is activated, the holding table 26 moves along the X-axis and / or Y-axis.

[0053] Furthermore, the perforated plate 26a is connected to a suction source (not shown) such as a vacuum pump through a flow path provided inside the holding stage 26. Then, if this suction source is activated, a negative pressure will be generated in the space near the holding surface of the holding stage 26.

[0054] Furthermore, a support structure 30 is provided in the area behind the base 4, the support structure 30 having a side surface that is substantially parallel to the Y-axis and Z-axis directions. A vertical movement mechanism 32 is arranged on the side surface of this support structure 30. The vertical movement mechanism 32 then has a pair of Z-axis guide rails 34 that are fixed to the side surface of the support structure 30 and extend along the Z-axis direction.

[0055] The Z-axis moving plate 36 is connected to the front side of a pair of Z-axis guide rails 34 in a manner that allows it to slide along the pair of Z-axis guide rails 34. Furthermore, a screw (not shown) extending along the Z-axis direction is disposed between the pair of Z-axis guide rails 34. A motor 38 for rotating the screw is connected to the upper end (one end) of this screw.

[0056] Furthermore, a nut portion (not shown) is provided on the surface of the screw shaft with helical grooves to form a ball screw. The nut portion accommodates multiple balls, which roll on the surface of the rotating screw shaft. That is, if the screw shaft rotates, the multiple balls will circulate within the nut portion, and the nut portion will move along the Z-axis direction.

[0057] Furthermore, this nut is fixed to the back side of the Z-axis moving plate 36. Therefore, if the screw shaft disposed between a pair of Z-axis guide rails 34 is rotated by the motor 38, the Z-axis moving plate 36 and the nut move together along the Z-axis direction.

[0058] A support 40 is fixed to the front side of the Z-axis moving plate 36. This support 40 supports a portion of the laser beam irradiation unit 42. Figure 5 is a schematic diagram showing the travel of the laser beam LB in the laser beam irradiation unit 42. Furthermore, in Figure 5, a portion of the constituent elements of the laser beam irradiation unit 42 is shown in a functional block diagram.

[0059] The laser beam irradiation unit 42 has a laser oscillator 44 fixed to the base 4. This laser oscillator 44 has, for example, Nd:YAG as the laser medium, and emits a laser beam LB with a wavelength (e.g., 1342 nm) that penetrates the wafer 11. This laser beam LB is, for example, a pulsed laser beam with a frequency of 60 kHz.

[0060] Furthermore, the laser beam LB, after its output is adjusted in attenuator 46, is supplied to spatial light modulator 48. In this spatial light modulator 48, the laser beam LB is split. For example, the spatial light modulator 48 splits the laser beam LB, which is adjusted in attenuator 46, into multiple focusing points with different positions (coordinates) in a plane (XY coordinate plane) parallel to the X-axis and Y-axis directions and / or different positions (heights) in the Z-axis direction.

[0061] Furthermore, the laser beam LB, which is branched in the spatial light modulator 48, is reflected by the mirror 50 and guided to the irradiation head 52. The irradiation head 52 houses a focusing lens (not shown) for focusing the laser beam LB. Then, the laser beam LB focused by this focusing lens is emitted to the holding surface side of the holding stage 26.

[0062] Furthermore, as shown in Figure 4, the irradiation head 52 is disposed at the front end of the cylindrical housing 54. Moreover, a support 40 is fixed to the rear side of this housing 54. Furthermore, a camera unit 56 is fixed to the front side of this housing 54.

[0063] This camera unit 56 includes, for example, a light source such as an LED (Light Emitting Diode), an objective lens, and camera elements such as a CCD (Charge Coupled Device) image sensor or a CMOS image sensor.

[0064] Then, if the aforementioned vertical movement mechanism 32 is activated, the laser beam irradiation unit 42 and the camera unit 56 move along the Z-axis. Furthermore, a cover (not shown) covering the aforementioned components is provided on the base 4. A touch panel 58 is disposed on the front surface of this cover.

[0065] This touch panel 58 is composed of an input device such as a capacitive or resistive touch sensor and a display device such as a liquid crystal display or an organic EL (Electro Luminescence) display, and functions as a user interface.

[0066] When forming a release layer inside the wafer 11 using the laser processing apparatus 2, firstly, the bonding wafer is placed on the holding stage 26 in such a way that the center of the holding surface of the holding stage 26 is aligned with the center of the back surface 17b supporting the wafer 17. Next, the suction source connected to the holding stage 26 is activated such that the bonding wafer is held by the holding stage 26.

[0067] Next, the camera unit 56 captures an image of the back side 11b of the wafer 11 that is attached to the wafer. Then, referring to this image, the horizontal movement mechanism 6 is activated such that the irradiation head 52 of the laser beam irradiation unit 42 is positioned directly above the area of ​​the wafer 11 that is slightly inside the outer periphery.

[0068] Furthermore, referring to this image, the rotation drive source connected to the lower part of the worktable base 24 can also be operated in the following manner: the holding stage 26 is rotated so that the crystal direction

[0010] of the single crystal silicon constituting the wafer 11 becomes parallel to the X-axis direction, and the crystal direction

[0001] becomes parallel to the Y-axis direction.

[0069] Next, a laser beam LB is irradiated into the annular first region of wafer 11 that is more inner than the outer peripheral region, thereby forming a first release layer. The first release layer becomes the starting point for separation between the region of wafer 11 where multiple elements 15 are formed and the outer peripheral region (first release layer formation step: S2).

[0070] In this first release layer formation step (S2), while the annular first region of the wafer 11, which is further inward than the outer peripheral region, has been irradiated with a laser beam LB, the holding stage 26 that holds the wafer 11 through the supporting wafer 17 is rotated. Figure 6 is a partial cross-sectional side view schematically showing the situation where the rotating wafer 11 is irradiated with a laser beam LB.

[0071] Specifically, in this first stripping layer formation step (S2), the wafer 11 is irradiated by a branched laser beam LB in such a way that multiple (e.g., 2 to 10) focusing points with different positions (heights) in the Z-axis direction are formed.

[0072] Among these multiple focusing points, for example, the lowest focusing point is positioned slightly higher than the front side 11a of wafer 11, and the highest focusing point is positioned at a height between the front side 11a and the back side 11b of wafer 11. Furthermore, the multiple focusing points are arranged such that their positions (heights) in the Z-axis direction are equally spaced (e.g., every 5μm to 15μm).

[0073] In this case, taking each of the multiple focal points as the center, a modified region 21 with disordered crystal structure is formed inside the wafer 11. Furthermore, cracks 23 extend from each of the multiple modified regions 21 in a manner that connects one pair of adjacent modified regions 21.

[0074] In this way, a release layer is formed inside the wafer 11, the release layer comprising a plurality of modified regions 21 and cracks 23 developing from each of the plurality of modified regions 21. Then, while maintaining the irradiation of the wafer 11 with a laser beam LB, the holding stage 26 holding the wafer in place rotates one revolution, thereby activating the rotation drive source connected to the lower part of the stage base 24.

[0075] As a result, a release layer (first release layer) is formed between the region where the plurality of elements 15 are formed on the wafer 11 and the peripheral region. This first release layer has, for example, a cylindrical shape as if along the side of a cylinder, with the lower bottom surface of the cylinder located on the front side 11a of the wafer 11 and the upper bottom surface located inside the wafer 11.

[0076] Next, a laser beam LB is irradiated onto a second region of wafer 11 that is further inward than the outer periphery, thereby forming a second release layer. This second release layer becomes the separation starting point between the front side 11a and the back side 11b of wafer 11 (second release layer formation step: S3). Figure 7 is a flowchart schematically showing an example of the second release layer formation step (S3).

[0077] In this second release layer formation step (S3), firstly, a laser beam LB is irradiated onto a straight area along the crystal direction

[0010] of the single-crystal silicon constituting the wafer 11 (laser beam irradiation step: S31). For example, when the bonding wafer is held on the holding stage 26 with the crystal direction

[0010] parallel to the X-axis direction, the laser beam LB is irradiated onto the wafer 11 while the holding stage 26 is moved along the X-axis direction.

[0078] Figure 8 is a partial cross-sectional side view schematically showing the situation of irradiating a laser beam LB onto a wafer 11 moving along the X-axis direction. In this laser beam irradiation step (S31), for example, the wafer 11 is irradiated by a branched laser beam LB in such a way that multiple (e.g., 2 to 10) focusing points are formed at different positions (coordinates) in the Y-axis direction.

[0079] These multiple focusing points are positioned, for example, at the same height as the uppermost modified region 21 among the multiple modified regions 21 contained in the first exfoliation layer. Furthermore, the multiple focusing points are arranged, for example, at equal intervals (e.g., every 5 μm to 15 μm) in the Y-axis direction.

[0080] In this situation, similar to the first stripping layer formation step (S2), multiple modified regions 21 and cracks 23 developing from each of the multiple modified regions 21 are formed inside the wafer 11. Then, while maintaining the irradiation of the wafer 11 with the laser beam LB, the horizontal movement mechanism 6 is activated in such a way that the holding stage 26 holding the wafer is moved along the X-axis.

[0081] As a result, a release layer 25 is formed in a linear region along the X-axis within a second region that is more inner than the outer periphery of the wafer 11. Here, the cracks 23 contained in this release layer 25 mostly extend along the crystal plane (k01) (k is an integer whose absolute value is less than 10, excluding 0). That is, when the wafer 11 is irradiated with a laser beam LB, the cracks 23 tend to extend along the following crystal plane. [Number 1] [Number 2]

[0082] Then, the acute angle formed by the crystal plane (100) and the crystal plane (k01) exposed on the front side 11a and the back side 11b of the wafer 11 is 45° or less. Therefore, if the direction of the crack 23 is decomposed into a component parallel to the front side 11a and the back side 11b of the wafer 11 (parallel component) and a component perpendicular to the front side 11a and the back side 11b (vertical component), the parallel component will be larger than the vertical component.

[0083] Next, the holding stage 26 is moved along the crystal direction

[0001] of the single-crystal silicon constituting wafer 11 (indexing feed step (S32)). For example, when the bonding wafer is held on the holding stage 26 with the crystal direction

[0001] of the single-crystal silicon constituting wafer 11 parallel to the Y-axis direction, the holding stage 26 is moved along the Y-axis direction.

[0084] Next, the laser beam irradiation unit 42 and the horizontal movement mechanism 6 are activated in such a way that the release layer 25 is formed in a straight line parallel to the straight line region where the release layer 25 has already been formed. That is, the laser beam irradiation step (S31) is performed again. Figure 9 is a schematic cross-sectional view of the adjacent release layers 25 formed inside the wafer 11 by performing two laser beam irradiation steps (S31).

[0085] In this case, a release layer 25 (release layer 25-2) is formed inside the wafer 11. The release layer 25 (release layer 25-2) is parallel to the release layer 25 (release layer 25-1) formed in the first laser beam irradiation step (S31) and separates from the release layer 25-1 in the Y-axis direction. Furthermore, the indexing feed step (S32) and the laser beam irradiation step (S31) are repeated in such a way that the release layer 25 is formed in the entire area of ​​the second region that is more inner than the outer peripheral region of the wafer 11 (from the region on one end to the region on the other end in the Y-axis direction).

[0086] Then, if a release layer 25 is formed over the entire second region of wafer 11 that is further inward than the outer periphery (step (S33): Yes), the second release layer formation step (S3) ends. As a result, a release layer (second release layer) is formed between the front side 11a and the back side 11b of wafer 11. This second release layer has, for example, a disk-shaped form like that along the top surface of a cylinder having sides along the aforementioned first release layer.

[0087] In the method shown in Figure 2, after performing the first release layer formation step (S2) and the second release layer formation step (S3), the wafer 11 is separated by applying external force to the wafer 11, using the first release layer and the second release layer as the separation starting point (separation step: S4).

[0088] Figures 10(A) and 10(B) are partial cross-sectional side views schematically illustrating the separation of wafer 11. This separation step (S4) is performed, for example, in the separation apparatus 60 shown in Figures 10(A) and 10(B). This separation apparatus 60 has a holding stage 62 for holding the bonded wafer, which includes the wafer 11 for which a first release layer and a second release layer have been formed.

[0089] The holding stage 62 has a circular upper surface (holding surface) in which a perforated plate (not shown) is exposed. Furthermore, this perforated plate is connected to a suction source (not shown) such as a vacuum pump through a flow path provided inside the holding stage 62. Then, if this suction source is activated, a negative pressure is generated in the space near the holding surface of the holding stage 62.

[0090] Furthermore, a separation unit 64 is provided above the holding platform 62. This separation unit 64 has a cylindrical support member 66. A ball screw type lifting mechanism (not shown) is connected to the upper part of this support member 66, for example, and the separation unit 64 is raised and lowered by operating this lifting mechanism.

[0091] Furthermore, the lower end of the support member 66 is fixed to the center of the upper part of the disc-shaped gripper base 68. On the lower side of the outer peripheral region of this gripper base 68, a plurality of grippers 70 are provided at approximately equal intervals along the circumferential direction of the gripper base 68. Each gripper 70 has a plate-shaped upright portion 70a extending downward.

[0092] The upper end of this erected part 70a is connected to an actuator such as a cylinder built into the gripper base 68. By actuating this actuator, the gripper 70 moves radially along the gripper base 68. Furthermore, a plate-shaped claw part 70b is provided on the inner side of the lower end of this erected part 70a. The claw part 70b extends toward the center of the gripper base 68 and becomes thinner as it gets closer to the center of the gripper base 68.

[0093] In the separation apparatus 60, for example, the separation step (S4) is performed in the following sequence. Specifically, firstly, the bonding wafer, which includes a wafer 11 having a first release layer and a second release layer, is placed on the holding stage 62 in such a way that the center of the back surface 17b of the support wafer 17 is aligned with the center of the holding surface of the holding stage 62.

[0094] Next, the attraction source, which communicates with the perforated plate exposed in the holding surface, is activated by holding the wafer in a manner that conforms to the holding stage 62. Then, the actuator is activated by positioning each of the plurality of gripping claws 70 radially outward from the gripping claw base 68.

[0095] Next, the lifting mechanism is activated such that the front ends of the claw portions 70b of each of the plurality of gripping claws 70 are positioned at a height corresponding to the adhesive 19 of the bonding wafer. Next, the actuator is activated such that the claw portions 70b contact the bonding wafer. Next, the lifting mechanism is activated such that the claw portions 70b are raised (see Figure 10(A)).

[0096] In this way, an upward external force is applied to the outer periphery of the wafer 11, that is, an external force along the thickness direction of the wafer 11. As a result, the cracks 23 contained in the first and second release layers will extend further to separate the area of ​​the wafer 11 in which multiple elements 15 are formed from the outer periphery, and separate its front side 11a side from its back side 11b side (see Figure 10(B)).

[0097] In the above wafer processing method, a laser beam LB is irradiated along the crystal direction

[0010] on a wafer 11 manufactured in such a way that the crystal plane (100) is exposed on the front side 11a and the back side 11b respectively, thereby forming a release layer (second release layer), which becomes the separation starting point between the front side 11a and the back side 11b of the wafer 11.

[0098] In this case, the number of cracks 23 extending from the modified region 21 along the crystal plane (k01) (where k is an integer whose absolute value is less than 10, excluding 0) increases. Then, the acute angle formed by the crystal plane (100) of the single-crystal silicon and the crystal plane (k01) is less than 45°. Therefore, in this wafer processing method, the component of the direction of crack 23 extending parallel to the front side 11a and back side 11b of the wafer 11 (parallel component) becomes greater than or equal to the perpendicular component (perpendicular component).

[0099] In this way, the spacing between adjacent modified regions 21 can be lengthened in this wafer processing method. As a result, the travel distance (indexing) in the indexing feed step (S32) can be lengthened, and the processing time (laser beam LB irradiation time) required to form the release layer 25 that serves as the separation starting point between the front side 11a and the back side 11b of the wafer 11 can be shortened.

[0100] Furthermore, in this wafer processing method, the crack 23 becomes less likely to extend from the release layer 25 toward the front side 11a of the wafer 11. As a result, the probability of damage to the device 15 can be reduced when separating the front side 11a and the back side 11b of the wafer 11.

[0101] Furthermore, the above-described wafer processing method is one aspect of the present invention, and the present invention is not limited to the above method. For example, in the present invention, after the first release layer and the second release layer are formed on the wafer 11, the front side 11a of the wafer 11 can also be bonded to the front side 17a of the supporting wafer 17. That is, in the present invention, the bonding step (S1) can also be performed after the first release layer formation step (S2) and the second release layer formation step (S3).

[0102] Furthermore, the structure of the laser processing apparatus used in this invention is not limited to the structure of the laser processing apparatus 2 described above. For example, this invention can also be implemented using a laser processing apparatus equipped with a horizontal moving mechanism, which moves the irradiation head 52 of the laser beam irradiation unit 42 along the X-axis and / or Y-axis directions respectively.

[0103] That is, in this invention, as long as the holding stage 26 holding the wafer 11 and the irradiation head 52 of the laser beam irradiation unit 42 emitting the laser beam LB can be moved relative to each other along the X-axis and Y-axis directions, there is no limitation on the structure used to achieve it.

[0104] Furthermore, in this invention, the order of the first peel layer forming step (S2) and the second peel layer forming step (S3) is not limited. That is, in this invention, the first peel layer forming step (S2) can also be performed after the second peel layer forming step (S3).

[0105] However, if a disk-shaped second release layer is formed inside the wafer 11 in the second release layer formation step (S3), there is a concern that it may be impossible or difficult to form a new release layer on the front side 11a of the wafer 11, which is closer to the second release layer than the second release layer.

[0106] Therefore, in this invention, it is preferable to perform the second release layer formation step (S3) after performing the first release layer formation step (S2). This ensures that the release layer (first release layer) is reliably formed, which serves as the starting point for separation between the region of the wafer 11 where the plurality of elements 15 are formed and the peripheral region.

[0107] Alternatively, in this invention, it is preferable that the second region of the wafer 11 forming the second release layer is located further inside than the first region forming the first release layer. Therefore, even if the first release layer forming step (S2) is performed after the second release layer forming step (S3), the first release layer can still be reliably formed.

[0108] Furthermore, in the first release layer formation step (S2) of the present invention, the shape of the first release layer is not limited as long as it can function as a separation starting point between the region of the wafer 11 where multiple elements 15 are formed and the peripheral region. For example, the first release layer may also be shaped like the side of a cylinder, with the lower bottom surface of the cylinder located on the front side 11a of the wafer 11 and the upper bottom surface located on the back side 11b of the wafer 11.

[0109] That is, the first release layer can also be formed to extend through both the front side 11a and the back side 11b of the wafer 11. However, if the first release layer has this shape, there is a concern that it may become residual material and scatter in the outer peripheral area of ​​the wafer 11 during the separation step (S4). Therefore, in the first release layer forming step (S2) of the present invention, it is preferable to form the first release layer in a manner that does not reach the back side 11b of the wafer 11.

[0110] Furthermore, the first release layer can also be shaped like the side of a frustum, with the lower base (first base) of the frustum located on the front side 11a of the wafer 11 and the upper base (second base), which has a shorter diameter than the lower base, located inside the wafer 11. This first release layer is formed, for example, by irradiating the wafer 11 with a laser beam LB in a manner that makes the formed focal point closer to the outer peripheral region and thus closer to the front side 11a of the wafer 11.

[0111] Figure 11 is a partial cross-sectional side view schematically showing the situation where a laser beam LB is irradiated onto a rotating wafer 11 to form a first release layer of this shape. Specifically, in forming this first release layer, firstly, a laser beam LB is irradiated onto the wafer 11 to form a plurality of (e.g., 8) focal points, wherein the positions of adjacent focal points in both the radial (perpendicular to the Z-axis direction) and thickness (Z-axis direction) directions of the wafer 11 are offset by only 10 μm inside the wafer 11.

[0112] In this case, taking each of the multiple light-gathering points as the center, a modified region 21 is formed inside the wafer 11. The modified region 21 is formed by the disordered crystal structure of the material constituting the wafer 11. That is, multiple modified regions 21 are formed as follows: when viewed from above, they are arranged in a straight line along the radial direction of the wafer 11, and the acute angle formed by this straight line and the front surface 11a of the wafer 11 is 45°.

[0113] Furthermore, the acute angle formed by the multiple modified regions 21 arranged in a straight line and the front side 11a of the wafer 11 is not limited to 45°. That is, it is also possible to form multiple focal points with different spacing in the radial direction and different spacing in the thickness direction of adjacent focal points to irradiate the wafer 11 with a laser beam LB.

[0114] Furthermore, the cracks 23 extend from each of the plurality of modified regions 21 in such a way that adjacent pairs of modified regions 21 are connected. This forms a release layer inside the wafer 11, the release layer comprising the plurality of modified regions 21 and the cracks 23 developing from each of the plurality of modified regions 21.

[0115] Next, the laser beam irradiation unit 42 is kept in operation so that the holding stage 26 holding the wafer is rotated one revolution, thereby activating the rotation drive source connected to the lower part of the worktable base 24.

[0116] As a result, a release layer (first release layer) is formed in an annular first region on the wafer 11 that is more inner than the outer peripheral region, as if along the side of a frustum, the lower bottom surface of which is located on the front side 11a of the wafer 11 and the upper bottom surface located inside the wafer 11.

[0117] In the case of forming this first release layer, when separating the wafer 11 in the separation device 60, the probability of the newly exposed side surface of the region where multiple elements 15 are formed coming into contact with the inner side surface of the outer peripheral region becomes lower. Furthermore, in this case, the crack 23 becomes easier to extend from the first release layer in the direction along the side surface of the frustum.

[0118] Therefore, in this case, the probability of crack 23 extending toward element 15 is also reduced, thus suppressing damage to element 15. Furthermore, in the case of forming this first release layer, it becomes easier to manufacture wafers using the area near the outer periphery of the front side 11a of wafer 11. Therefore, in this case, the number of wafers that can be manufactured from wafer 11 can be increased.

[0119] Furthermore, in the first release layer formation step (S2) of the present invention, in addition to the rotation drive source connected to the lower part of the worktable base 24, the laser beam LB can also be irradiated onto the wafer 11 while the horizontal movement mechanism 6 and the vertical movement mechanism 32 are operated. Alternatively, the laser beam LB can be irradiated onto the wafer 11 while the horizontal movement mechanism 6 and the vertical movement mechanism 32 are operated, replacing the rotation drive source connected to the lower part of the worktable base 24. That is, not only can the wafer 11 be rotated, but the coordinates and height of the focusing point in the XY coordinate plane can also be changed while the laser beam LB is irradiated onto the wafer 11.

[0120] Furthermore, in the first release layer formation step (S2) of the present invention, multiple laser beams LB with the same or close focal points can be applied. In this case, the size of the modified region 21 contained in the release layer becomes larger, and the cracks 23 contained in the release layer extend further. Therefore, in this case, the separation of the wafer 11 in the separation step (S4) becomes easier.

[0121] Furthermore, in the first release layer formation step (S2) of the present invention, the laser beam LB can be irradiated onto the wafer 11 in such a way that adjacent modified regions 21 are not connected by cracks 23 but are directly connected to each other. In this case, since the shape of the release layer can be determined without depending on the shape of the cracks 23 that develop from the modified regions 21, the wafer 11 can be processed stably.

[0122] Furthermore, in the laser beam irradiation step (S31) of the second release layer formation step (S3) of the present invention, the area irradiated by the laser beam LB is not limited to a straight area along the crystal direction

[0010] of the single crystal silicon constituting the wafer 11. For example, in this laser beam irradiation step (S31), the laser beam LB can also be irradiated to a straight area along the crystal direction

[0001] .

[0123] Furthermore, when the laser beam LB is irradiated onto the wafer 11 in this way, the crack 23 becomes more likely to extend on the following crystal plane. [Number 3] [Number 4]

[0124] Furthermore, in this invention, a laser beam LB can also be irradiated onto a straight area that is only slightly inclined from the crystal direction

[0010] or the crystal direction

[0001] when viewed from above. This point will be explained with reference to FIG12.

[0125] Figure 12 is a graph showing the width (length of the direction orthogonal to the direction of extension of the linear region) of the lift-off layer formed inside the wafer 11 when a laser beam LB is irradiated onto a linear region along different crystal directions. Furthermore, the horizontal axis of this graph represents the angle formed by the direction of extension of the linear region (reference region) orthogonal to the crystal direction

[0011] when viewed from above, and the direction of extension of the linear region (measurement region) that is the object of measurement.

[0126] That is, when the horizontal axis of this graph is 45°, the linear area along the crystal direction

[0001] becomes the measurement object. Similarly, when the horizontal axis of this graph is 135°, the linear area along the crystal direction

[0010] becomes the measurement object. Furthermore, the vertical axis of this graph represents the value when the width of the stripping layer formed in the measurement area by irradiating the measurement area with a laser beam LB is divided by the width of the stripping layer formed in the reference area by irradiating the reference area with a laser beam LB.

[0127] As shown in Figure 12, the width of the release layer increases when the angle formed by the direction of extension of the reference region and the direction of extension of the measurement region is 40°~50° or 130°~140°. That is, the width of the release layer increases not only when a laser beam LB is irradiated along a straight area with an angle of less than 5° relative to the crystal direction

[0001] or crystal direction

[0010] .

[0128] Therefore, in the laser beam irradiation step (S31) of the second stripping layer formation step (S3) of the present invention, a laser beam LB can also be irradiated on a straight area that is tilted at less than 5° from the crystal direction

[0001] or the crystal direction

[0010] when viewed from above.

[0129] That is, in this laser beam irradiation step (S31), a laser beam LB can also be irradiated on a straight area along the following direction: parallel to and relative to the crystal direction of the specific crystal planes contained in the crystal plane {100}, the crystal planes exposed on the front side 11a and back side 11b of the wafer 11 (here, crystal plane (100)). <100> The angle formed by the specific crystal orientation (here, crystal orientation

[0001] or crystal orientation

[0010] ) is less than 5° (first orientation).

[0130] Furthermore, in the case where the laser beam irradiation step (S31) is performed in this way, the indexing feed step (S32) is performed by moving the position inside the wafer 11, which is formed by irradiating the laser beam LB, along a direction (second direction) that is parallel to and orthogonal to the first direction and is in the direction of the crystal plane (100) exposed on the front side 11a and back side 11b of the wafer 11, which is contained in the specific crystal plane {100}.

[0131] Furthermore, in the second release layer formation step (S3) of the present invention, after the release layer 25 is formed in the entire area of ​​the second region (from the region on one end to the region on the other end in the Y-axis direction) of the wafer 11 which is more inner than the outer peripheral region (step S33: yes), the laser beam irradiation step (S31) and the indexing feed step (S32) are repeated again.

[0132] That is, the second region where the release layer 25 has been formed can also be irradiated again with the same laser beam LB as when the release layer 25 was formed. In this case, the density of the modified region 21 and the crack 23 contained in the release layer 25 increases. As a result, the separation of the wafer 11 in the separation step (S4) becomes easier.

[0133] Furthermore, in the second release layer formation step (S3) of the present invention, the laser beam irradiation step (S31) can also be performed again after the laser beam irradiation step (S31) and before the indexing feed step (S32). That is, the linear region where the release layer 25 has been formed can also be irradiated again with the laser beam LB as in forming the release layer 25. In this case, as described above, the separation of the wafer 11 in the separation step (S4) becomes easier.

[0134] Furthermore, in the separation step (S4) of the present invention, ultrasound can also be applied to the wafer 11 before separating the wafer 11 on which the first release layer and the second release layer are formed. In this case, the cracks 23 contained in the first release layer and the second release layer will extend, thus making the separation of the wafer 11 easier.

[0135] Furthermore, in the separation step (S4) of the present invention, a device other than the separation device 60 described above can also be used to separate the wafer 11. For example, in the separation step (S4) of the present invention, after separating the region of the wafer 11 in which a plurality of elements 15 are formed from the peripheral region, the front side 11a side and the back side 11b side of the wafer 11 can also be separated.

[0136] The following description refers to Figures 13-15, illustrating an example of this separation step (S4). Figure 13 is a schematic top view of the wafer 11 provided to this separation step (S4). Prior to the bonding step (S1) described above, a plurality of cuts 11d extending radially along the outer periphery of the wafer 11 are formed.

[0137] Apart from the portion with notch 13, the plurality of cuts 11d are formed at approximately equal intervals along the circumferential direction of wafer 11. Then, each of the plurality of cuts 11d is formed such that the portion of wafer 11 radially inward reaches the first release layer formed in the first release layer formation step (S2) described above.

[0138] Furthermore, the first release layer formed inside this wafer 11 has a shape similar to that along the side of a cylinder, with the lower bottom surface of the cylinder located on the front side 11a of the wafer 11 and the upper bottom surface located on the back side 11b of the wafer 11. That is, in this wafer 11, a first release layer is formed that extends through both the front side 11a and the back side 11b of the wafer 11.

[0139] Furthermore, the multiple nicks 11d are formed, for example, by cutting the wafer 11 in a conventional dicing apparatus. Alternatively, the multiple nicks 11d can also be formed by irradiating the wafer 11 with a laser beam that produces laser ablation in a conventional laser processing apparatus.

[0140] Furthermore, in the outer peripheral region of wafer 11, a plurality of release layers extending radially along wafer 11 may be formed to replace the plurality of cuts 11d. In addition, this release layer is formed, for example, by a method similar to that used to form the first release layer and the second release layer described above.

[0141] Figures 14(A) and 14(B) are schematic partial cross-sectional side views showing the separation of the region where multiple elements 15 are formed from the outer peripheral region of the wafer 11 shown in Figure 13. This separation of the wafer 11 is performed using the expansion device 72 shown in Figures 14(A) and 14(B).

[0142] This expansion device 72 has a fixed cylindrical drum 74. A support unit 76 is provided around this drum 74. This support unit 76 has an annular support platform 78 arranged to surround the upper end of the drum 74. On this support platform 78, a plurality of clamps 80 are provided at approximately equal intervals along the circumference of the support platform 78.

[0143] Furthermore, below the support platform 78, multiple cylinders are arranged at approximately equal intervals along the circumference of the support platform 78, and the upper end of the piston rod 82 of each cylinder is fixed to the lower part of the support platform 78. Therefore, in the expansion device 72, by actuating the multiple cylinders, the support platform 78 and the multiple clamps 80, together with the piston rods 82, can be raised and lowered together.

[0144] When separating the region where multiple components 15 are formed from the peripheral region of the wafer 11 shown in FIG. 13, firstly, the annular frame 29 is attached to the peripheral region of one side of the disk-shaped extended film 27, and then the back side 11b of the wafer 11 is attached to its central region. In this way, a frame unit is formed by integrating the bonding wafer 11 and the supporting wafer 17 with the annular frame 29.

[0145] Next, multiple cylinders are actuated such that the upper surface of the support stage 78 and the upper end of the drum 74 are on the same plane. Then, the annular frame 29 is placed on the support stage 78 through the wafer spreader 27. That is, the frame unit is placed on the support stage 78 such that the supporting wafer 17 is facing upwards.

[0146] Next, the annular frame 29 is fixed by multiple clamps 80 (see Figure 14(A)). Then, multiple cylinders are actuated to lower the annular frame 29, which is fixed by the multiple clamps 80. In this way, the central region of the wafer expander film 27 is expanded only by the amount by which the annular frame 29 has been lowered, along the radial direction of the wafer 11.

[0147] At this time, a force directed radially outward toward the wafer 11 is applied to the wafer 11 which has been attached to the expander film 27. As a result, the first release layer becomes the separation starting point and the area of ​​the wafer 11 where multiple elements 15 are formed is separated from the peripheral area (see Figure 14(B)).

[0148] Figures 15(A) and 15(B) are schematic partial cross-sectional side views illustrating the separation of the front 11a side and the back 11b side of the wafer 11 shown in Figure 14(B). This separation of the wafer 11 is performed using the separation apparatus 84 shown in Figures 15(A) and 15(B). This separation apparatus 84 has a holding stage 86 for holding the bonded wafer, including the wafer 11 shown in Figure 14(B).

[0149] The holding stage 86 has a circular upper surface (holding surface) in which a perforated plate (not shown) is exposed. Furthermore, this perforated plate is connected to a suction source (not shown) such as a vacuum pump through a flow path provided inside the holding stage 86. Therefore, if this suction source is activated, a negative pressure is generated in the space near the holding surface of the holding stage 86.

[0150] Furthermore, a separation unit 88 is provided above the holding platform 86. This separation unit 88 has a cylindrical support member 90. A ball screw type lifting mechanism (not shown) is connected to the upper part of this support member 90, for example, and the separation unit 88 is raised and lowered by actuating this lifting mechanism.

[0151] Furthermore, the lower end of the support member 90 is fixed to the center of the upper part of the disc-shaped suction plate 92. Multiple suction ports are formed on the lower surface of this suction plate 92, and each of these ports is connected to a suction source (not shown) such as a vacuum pump through a flow path provided inside the suction plate 92. Therefore, if this suction source is activated, a negative pressure is generated in the space near the lower surface of the suction plate 92.

[0152] When separating the front 11a side and the back 11b side of the wafer 11 shown in FIG. 14(B), firstly, the bonding wafer containing the wafer 11 is removed from the expander film 27. Next, the bonding wafer is placed on the holding stage 86 in such a way that the center of the back 17b of the supporting wafer 17 is aligned with the center of the holding surface of the holding stage 86.

[0153] Next, the suction source, which communicates with the perforated plate exposed in the holding surface, is activated so that the wafer is held in place by the holding stage 86. Then, the lifting mechanism is activated so that the lower surface of the suction plate 92 contacts the back surface 11b of the wafer 11, thereby lowering the separation unit 88.

[0154] Next, the attraction source connected to the multiple attraction ports is activated so that the wafer 11 is attracted to the back side 11b side through the multiple attraction ports formed on the attraction plate 92. Then, the lifting mechanism is activated so that the separation unit 88 is raised by moving the attraction plate 92 away from the holding stage 86 (see Figure 15(A)).

[0155] At this time, the upward force along the thickness direction of wafer 11 will act on the back side 11b side of wafer 11 that has been attracted through the multiple attraction ports formed on attraction plate 92. As a result, the second release layer becomes the separation starting point, and the front side 11a side and the back side 11b side of wafer 11 are separated (see Figure 15(B)).

[0156] Furthermore, the structure and method of the above-described embodiments can be appropriately modified and implemented as long as they do not depart from the scope of the purpose of this invention.

[0157] 11: Wafer 11a: Front 11b: Back 11c: Side view 11d: Incision 13: Gap 15: Components 17: Supporting the wafer 17a: Front 17b: Reverse side 19: Adhesive 21: Modified Area 23: Cracks 25, 25-1, 25-2: Peel-off layers 27: Expanding film 29: Ring-shaped frame 2: Laser processing equipment 4:Abutment 6: Horizontal moving mechanism 8: Y-axis guide rail 10: Y-axis moving plate 12: Screw 14: Motor 16: X-axis guide rail 18: X-axis moving plate 20: Screw 22: Motor 24: Workbench Base 26: Keep the platform 26a: Perforated plate 30: Support structure 32: Vertical moving mechanism 34: Z-axis guide rail 36: Z-axis moving plate 38: Motor 40: Support 42: Laser beam illumination unit 44: Laser Oscillator 46: Attenuator 48: Spatial Light Modulator 50: Mirror 52: Irradiation head 54: Outer shell 56: Camera Unit 58: Touch panel 60: Separation device 62: Keep the platform 64: Separation Unit 66: Supporting components 68: Grip Claw Base 70: Grip Claw 70a: Establishment Department 70b: Claws 72: Expansion device 74: Drum Wheel 76: Support Unit 78: Support platform 80: Fixture 82: Piston rod 84: Separation device 86: Keep the platform 88: Separation Unit 90: Supporting components 92: Attraction board

Claims

1. A method for processing a single-crystal silicon wafer, wherein a laser beam having a wavelength that can penetrate single-crystal silicon is used to irradiate a single-crystal silicon wafer manufactured in a manner that exposes specific crystal faces contained in crystal face {100} on the front and back sides respectively, and the outer peripheral region is chamfered, wherein a laser beam is positioned inside the single-crystal silicon wafer by irradiating a laser beam formed thereon, and the single-crystal silicon wafer is separated from the single-crystal silicon wafer using the laser beam as a separation starting point, the single-crystal silicon wafer processing method comprising: a first release layer forming step, wherein the laser beam is irradiated from the back side of the single-crystal silicon wafer on a first annular region of the single-crystal silicon wafer that is more inner than the outer peripheral region, thereby forming a first release layer, the first release layer being the separation starting point when separating the outer peripheral region from the single-crystal silicon wafer; The second release layer formation step involves irradiating a second region, which is further inward than the outer peripheral region, of the single-crystal silicon wafer from the back side of the wafer with a laser beam, thereby forming a second release layer. This second release layer serves as the separation starting point between the front and back sides of the single-crystal silicon wafer. The separation step, following the first and second release layer formation steps, involves applying external force to the single-crystal silicon wafer to separate it using the first and second release layers as separation starting points. In the second release layer formation step, the second release layer is formed by repeatedly performing a laser beam irradiation step and a indexing feed step. The laser beam irradiation step involves moving the single-crystal silicon wafer relative to the focal point along a first direction parallel to the specific crystal plane while irradiating the linear region along the first direction within the second region with the laser beam. The indexing feed step moves the internal position of the single-crystal silicon wafer, which forms the focal point by irradiating the laser beam, along a second direction that is parallel to the specific crystal plane and orthogonal to the first direction.

2. The method for processing a single-crystal silicon wafer as described in claim 1, wherein, The angle formed by the first direction relative to the specific crystal direction contained in the crystal direction <100> is 5° or less.

3. The method for processing a single-crystal silicon wafer as described in claim 1, wherein, Multiple elements are formed on the front side of the single-crystal silicon wafer.

4. The method for processing a single-crystal silicon wafer as claimed in claim 1, further comprising: a bonding step, wherein, before performing the first release layer forming step and the second release layer forming step, the front side of the single-crystal silicon wafer is bonded to the front side of a support wafer.

5. The method for processing single-crystal silicon wafers as described in claim 4, wherein, Multiple elements are formed on the front side of the supporting wafer.

6. A method for processing a single-crystal silicon wafer as described in claim 1, wherein, The first release layer includes multiple modified regions, each of which is located between the front side of the single-crystal silicon wafer and the second release layer in the thickness direction of the single-crystal silicon wafer, and is positioned differently from each other in the thickness direction.

7. A method for processing a single-crystal silicon wafer as described in claim 1, wherein, The first release layer formation step is performed before the second release layer formation step.

8. A method for processing a single-crystal silicon wafer as described in claim 1, wherein, The second region is located further inside than the first region.

9. A method for processing a single-crystal silicon wafer as described in claim 1, wherein, In the first release layer formation step, the first release layer is formed in a manner that does not reach the back side of the single-crystal silicon wafer.

10. A method for processing a single-crystal silicon wafer as described in any of claims 1 to 9, wherein, In the first release layer formation step, the laser beam is irradiated in such a way that the spotting point is closer to the outer peripheral region and thus closer to the front side of the single-crystal silicon wafer, thereby forming the first release layer as if along the side of a frustum. The first bottom surface of the frustum is located on the front side of the single-crystal silicon wafer, and the second bottom surface, which has a diameter shorter than the first bottom surface, is located inside the single-crystal silicon wafer.

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