Method for processing a single crystal silicon wafer

Abstract

Provided is a method for processing a single crystal silicon wafer, which can shorten the processing time when the wafer is separated using a separation layer formed in the wafer as a separation starting point after the separation layer is formed, and can reduce the probability of damage to the device. For a single crystal silicon wafer manufactured in such a manner that a specific crystal plane (for example, a crystal plane (100)) included in a crystal plane {100} is exposed on the front surface and the back surface, respectively, a laser beam is irradiated along a first direction parallel to the specific crystal plane and making an angle of 5° or less with a specific crystal direction (for example, a crystal direction [010]) included in a crystal direction <100>, thereby forming a separation layer as a separation starting point between the front surface side and the back surface side of the single crystal silicon wafer.

Description

Technical Field

[0001] This invention relates to a method for processing monocrystalline silicon wafers, wherein after a release layer is formed inside the monocrystalline silicon wafer, the monocrystalline silicon wafer is separated using the release layer as the starting point for separation. Background Technology

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

[0003] In addition, for the purpose of high integration such as packaging that includes multiple chips, through-silicon vias (TSVs) are sometimes provided on the wafer. In such packages, for example, electrodes contained in different chips can be electrically connected by means of TSVs.

[0004] The TSV is disposed on the wafer in the following order, for example. First, a groove is formed on the front side of the wafer. Next, the TSV is disposed in the 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] Here, in wafers, the outer periphery is often chamfered to prevent breakage. Furthermore, when the back side of a wafer with a chamfered outer periphery is ground to less than half the wafer thickness, the back side of that outer periphery becomes a blade-like shape.

[0006] In this case, during the wafer grinding process, stress concentrates on the back side of the outer peripheral region, making the wafer prone to breakage and raising concerns about a decrease in the yield of chips obtained from the wafer. Therefore, a solution has been proposed that a portion of the front side of the outer peripheral region be removed (so-called edge trimming) before grinding the back side of such a wafer (see, for example, Patent Document 1).

[0007] Therefore, when removing the remaining portion of the back side of the outer peripheral region through grinding, the side surface of the wafer is approximately perpendicular to both the front and back sides. Consequently, no stress concentration occurs on the back side of the outer peripheral region during wafer grinding, reducing the likelihood of wafer breakage. As a result, it is possible to suppress any reduction in chip yield.

[0008] However, after edge trimming, grinding the back side of the wafer until the TSV is exposed on the back side increases the amount of grinding required, leading to increased wear on the grinding tools. This increases the cost of the chip or package manufactured using the wafer and raises concerns about the long processing time.

[0009] In view of this point, the following method is proposed: after the formed focusing point is positioned inside the wafer and a laser beam with a wavelength that can penetrate the wafer is irradiated onto the wafer, thereby forming a release layer inside the wafer, the wafer is separated using the release layer as the separation starting point (see, for example, Patent Document 2).

[0010] In this method, a laser beam is first irradiated onto a first annular region of the wafer that does not produce diffuse reflection when irradiated with the laser beam (in short, an annular region inside the chamfered outer peripheral region). This forms a release layer (cylindrical release layer) that serves as the starting point for separation between the device-forming region and the outer peripheral region of the wafer.

[0011] Next, the laser beam is irradiated into a second region of the wafer that does not produce diffuse reflection when irradiated with the laser beam (in short, a circular region that is inside the chamfered outer periphery). This forms a release layer (a disk-shaped release layer) that serves as 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 at the cylindrical and disk-shaped release layers. That is, the peripheral region of the wafer is separated from the area where the device is formed, and the back side is separated from the front side of the wafer.

[0013] By separating the wafer in this way, the amount of wafer grinding required until the TSV is exposed on the back side of the wafer can be reduced, and the wear of the grinding tools required to grind the wafer can be reduced. As a result, it is possible to suppress the increase in cost of chips or packages manufactured using the wafer, and to shorten the time required for wafer grinding.

[0014] Patent Document 1: Japanese Patent Application Publication No. 2007-158239

[0015] Patent Document 2: Japanese Patent Application Publication No. 2020-136442

[0016] The aforementioned release layer comprises: a modified region in which the crystal structure of the monocrystalline silicon constituting the wafer is disrupted; and cracks extending from the modified region. Specifically, when the aforementioned laser beam is irradiated onto the wafer, a modified region is formed inside the wafer centered on the focal point of the laser beam. Furthermore, cracks extend from the modified region along a predetermined crystal plane of the monocrystalline silicon constituting the wafer.

[0017] Here, single-crystal silicon is typically most easily cleaved on a specific crystal plane contained in crystal plane {111}. For example, for a wafer manufactured in such a manner that a specific crystal plane contained in crystal plane {100} (e.g., crystal plane (100)) is exposed on the front and back sides respectively, when along the crystal orientation... <110> When a laser beam is irradiated with a crystal direction (e.g., crystal direction

[011] ) that is parallel to the specific crystal plane in the specific crystal direction contained therein, a large number of cracks are generated extending from the modified region along the specific crystal plane (e.g., crystal plane (111)) contained in the crystal plane {111}.

[0018] Furthermore, the acute angle between a specific crystal plane (e.g., crystal plane (100)) included in the crystal plane {100} of the monocrystalline silicon and a specific crystal plane (e.g., crystal plane (111)) included in the crystal plane {111} is approximately 54.7°. Therefore, when a laser beam is irradiated onto the wafer as described above, a large number of cracks extending from the modified region are generated in a direction inclined at approximately 54.7° relative to the front or back side of the wafer.

[0019] That is, when the direction of such crack propagation 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 (vertical component), the vertical component is greater than the parallel component. Therefore, when a release layer (disc-shaped release layer) is formed by irradiating the wafer with a laser beam as described above, serving as the separation starting point between the front and back sides of the wafer, the following problem is concerned.

[0020] First, in this case, the parallel component of the crack propagation direction is relatively small. Therefore, in order to connect adjacent modified regions using cracks, it is necessary to narrow the interval between adjacent modified regions. Furthermore, narrowing the interval between adjacent modified regions requires extending the processing time (laser beam irradiation time) required to form the disk-shaped release layer.

[0021] Furthermore, in this case, the vertical component of the crack propagation direction is relatively large, raising concerns that the crack may extend from the disc-shaped release layer towards the front side of the wafer, potentially causing device breakage. Additionally, while forming a disc-shaped release layer sufficiently far from the front side of the wafer can reduce the probability of device breakage, this increases the amount of grinding required during subsequent wafer grinding. Summary of the Invention

[0022] In view of the above points, the object of the present invention is to provide a method for processing single-crystal silicon wafers that can shorten the processing time when the wafer is separated by using the release layer as the separation starting point after the release layer is formed inside the wafer, and can reduce the probability of device breakage.

[0023] According to the present invention, a method for processing a single-crystal silicon wafer is provided. For a single-crystal silicon wafer manufactured such that specific crystal planes included in crystal plane {100} are exposed on both the front and back sides, and multiple devices are formed on the front side and the outer peripheral region is chamfered, after a release layer is formed inside the single-crystal silicon wafer by irradiating a laser beam with a wavelength that transmits through the single-crystal silicon and a focal point located inside the wafer, the single-crystal silicon wafer is separated using this release layer as a separation starting point. The method for processing the single-crystal silicon wafer includes the following steps: a bonding step, in which the front side of the single-crystal silicon wafer is bonded to the front side of a support 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 inward from the outer peripheral region, thereby forming the single-crystal silicon wafer. The process involves: a first release layer forming a region containing the plurality of devices and the outer peripheral region; a second release layer forming step, in which a laser beam is irradiated from the back side of the single-crystal silicon wafer in a second region of the single-crystal silicon wafer that is inward of the outer peripheral region, thereby forming a second release layer as 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 the bonding step, the first release layer forming step, and the second release layer forming step, an external force is applied to the single-crystal silicon wafer, thereby separating the single-crystal silicon wafer using the first release layer and the second release layer as separation starting points. In the second release layer forming step, the second release layer is formed by repeatedly performing the laser beam irradiation step and the indexing feed step, wherein, in the laser beam irradiation step, the laser beam is applied along a direction parallel to the specific crystal plane and relative to the crystal orientation. <100> A first direction, with an angle of 5° or less formed by the specific crystal orientation, moves the single-crystal silicon wafer and the focal point relative to each other while irradiating the linear region along the first direction included in the second region with the laser beam. In the indexing feed step, the position of the focal point formed by the irradiation of the laser beam inside the single-crystal silicon wafer is moved along a second direction that is parallel to the specific crystal plane and perpendicular to the first direction.

[0024] In addition, it is preferable that the first release layer formation step is performed before the second release layer formation step.

[0025] In addition, it is preferable that the second region is located inside the first region.

[0026] In addition, 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.

[0027] In addition, preferably in the first release layer formation step, the laser beam is irradiated in such a way that the spotting point formed 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 along the side of the truncated cone, wherein the first bottom surface of the truncated cone is located on the front side of the single crystal silicon wafer and the second bottom surface, which is shorter in diameter than the first bottom surface, is located inside the single crystal silicon wafer.

[0028] In this invention, for a single-crystal silicon wafer manufactured such that a specific crystal plane (e.g., crystal plane (100)) contained in crystal plane {100} is exposed on the front and back sides respectively, along a path parallel to and relative to the crystal orientation of that specific crystal plane... <100> A laser beam is irradiated in a first direction with an angle of 5° or less to a specific crystal orientation (e.g., crystal orientation

[010] ), thereby forming a release layer (second release layer) that serves as the starting point for separation between the front and back sides of a single-crystal silicon wafer.

[0029] In this case, for cracks extending from the modified region, the number of cracks along specific crystal planes (e.g., crystal plane (101)) contained in crystal plane {n10} (where n is a natural number less than 10) increases compared to cracks along specific crystal planes contained in crystal plane {111} (e.g., crystal plane (111)). Furthermore, the acute angle between the specific crystal plane contained in crystal plane {100} and the specific crystal plane contained in crystal plane {n10} is 45° or less.

[0030] Therefore, in this invention, for a single-crystal silicon wafer manufactured such that a specific crystal plane included in crystal plane {100} is exposed on the front and back sides respectively, and along a direction parallel to that specific crystal plane and included in the crystal orientation... <110> Compared to the case where a second release layer is formed by irradiating a laser beam with a specific crystal orientation (e.g., crystal orientation

[011] ), the component of the direction of crack propagation that is parallel to the front and back sides of the wafer (parallel component) increases, while the component perpendicular to the wafer (vertical component) decreases.

[0031] Therefore, in this invention, the parallel component of the crack propagation direction is increased, thus extending the interval between adjacent modified regions. As a result, the travel distance (indexing amount) in the indexing feed step can be extended, and the processing time (laser beam irradiation time) required to form the release layer that serves as the separation starting point between the front and back sides of the wafer can be shortened.

[0032] Furthermore, in this invention, the vertical component of the crack propagation direction is reduced, thus making it less likely for cracks to propagate from the release layer toward the front side of the wafer. As a result, the probability of device breakage can be reduced when separating the front and back sides of the wafer. Attached Figure Description

[0033] Figure 1(A) is a schematic top view illustrating an example of a wafer. Figure 1 (B) is a cross-sectional view schematically showing an example of a wafer.

[0034] Figure 2 This is a flowchart illustrating an example of a wafer fabrication method.

[0035] Figure 3 This is a schematic cross-sectional view showing the front side of a wafer being attached to the front side of a support wafer.

[0036] Figure 4 This is a perspective view schematically illustrating an example of a laser processing apparatus.

[0037] Figure 5 This is a schematic diagram illustrating the travel of a laser beam within a laser beam irradiation unit.

[0038] Figure 6 This is a schematic partial cross-sectional side view illustrating the situation of a rotating wafer being irradiated with a laser beam.

[0039] Figure 7 This is a flowchart illustrating an example of the second peeling layer formation step.

[0040] Figure 8 This is a schematic partial cross-sectional side view illustrating the situation of irradiating a wafer moving along the X-axis with a laser beam.

[0041] Figure 9 This is a schematic cross-sectional view showing adjacent peeling layers formed inside the ingot.

[0042] Figure 10 (A) and Figure 10 (B) is a partial cross-sectional side view schematically showing the separation of the wafers.

[0043] Figure 11 This is a schematic partial cross-sectional side view illustrating the situation of a rotating wafer being irradiated with a laser beam.

[0044] Figure 12 It is a graph showing the width of the release layer formed inside the wafer when a laser beam is irradiated into a linear region along different crystal orientations.

[0045] Figure 13 This is a top view schematically showing a modified example of a wafer.

[0046] Figure 14 (A) and Figure 14 (B) is a partial cross-sectional side view schematically showing the separation of the region of the wafer in which multiple devices are formed from the peripheral region.

[0047] Figure 15 (A) and Figure 15 (B) is a partial cross-sectional side view schematically showing the separation of the front and back sides of the wafer.

[0048] Label Explanation

[0049] 11: Wafer (11a: Front, 11b: Back, 11c: Side, 11d: Cut); 13: Notch; 15: Device; 17: Supporting wafer (17a: Front, 17b: Back); 19: Adhesive; 21: Modified area; 23: Crack; 25 (25-1, 25-2): Release layer; 27: Extension band; 29: Annular frame; 2: Laser processing device; 4: Base; 6: Horizontal moving mechanism; 8: Y-axis guide rail; 10: Y-axis moving plate; 12: Lead screw; 14: Motor; 16: X-axis guide rail; 18: X-axis moving plate; 20: Lead screw; 22: Motor; 24: Worktable base; 26: Holding worktable (26a: Perforated plate); 30: Support structure; 32: Vertical moving mechanism Structure; 34: Z-axis guide rail; 36: Z-axis moving plate; 38: motor; 40: support component; 42: laser beam irradiation unit; 44: laser oscillator; 46: attenuator; 48: spatial light modulator; 50: reflector; 52: irradiation head; 54: housing; 56: imaging unit; 58: touch panel; 60: separation device; 62: holding table; 64: separation unit; 66: support component; 68: gripper base; 70: gripper (70a: erection part, 70b: gripper part); 72: extension device; 74: drum; 76: support unit; 78: support platform; 80: clamp; 82: piston rod; 84: separation device; 86: holding table; 88: separation unit; 90: support component; 92: suction plate. Detailed Implementation

[0050] The embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 (A) is a top view schematically showing an example of a wafer (single-crystal silicon wafer). Figure 1 (B) is a schematic cross-sectional view illustrating an example of a wafer (single-crystal silicon wafer). Additionally, in Figure 1 In (A), the crystal orientation of the monocrystalline silicon constituting the wafer is also shown.

[0051] Figure 1 (A) and Figure 1 The wafer 11 shown in (B) is composed of cylindrical monocrystalline silicon with specific crystal planes (here, for ease of explanation, referred to as crystal planes (100)) exposed on the front side 11a and the back side 11b, respectively. That is, the wafer 11 is composed of cylindrical monocrystalline silicon with the vertical lines (crystal axes) of the front side 11a and the back side 11b along the crystal direction

[100] .

[0052] Furthermore, although the wafer 11 is manufactured such that the crystal plane (100) is exposed on the front side 11a and the back side 11b respectively, due to processing errors during manufacturing, the front side 11a and the back side 11b may each be a surface that is slightly inclined from the crystal plane (100). Specifically, the front side 11a and the back side 11b of the wafer 11 may each be a surface with an acute angle of 1° or less formed with the crystal plane (100).

[0053] That is, the crystal axis of wafer 11 can be along a direction with an acute angle of less than 1° formed with the crystal orientation

[100] . 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 at the crystal orientation

[100] . <110> The specific crystal planes contained therein (here, for ease of explanation, they are referred to as crystal orientations

[011] ).

[0054] In addition, the chip 11 is divided into multiple regions by multiple intersecting predetermined dividing lines, and devices such as IC (Integrated Circuit) and LSI (Large Scale Integration), semiconductor memory or CMOS (Complementary Metal Oxide Semiconductor) image sensors are formed on the front side 11a of each region.

[0055] Additionally, a groove for setting TSVs can be formed on the front side 11a of the wafer 11. Furthermore, the outer peripheral region of the wafer 11 is chamfered. That is, the side surface 11c of the wafer 11 is bent in a way that protrudes outwards. Also, no devices 15 are formed in the outer peripheral region of the wafer 11. That is, the area of ​​the wafer 11 where multiple devices 15 are formed is surrounded by the outer peripheral region.

[0056] Figure 2 This is a flowchart illustrating an example of a wafer fabrication method. In short, in this method, after a release layer is formed inside the wafer 11 by positioning a formed focal point inside the wafer 11 and irradiating the wafer 11 with a laser beam having a wavelength that can penetrate the wafer 11, the wafer 11 is separated using this release layer as the separation starting point.

[0057] Specifically, in this method, the front side 11a of the wafer 11 is first attached to the front side of the supporting wafer (attachment step: S1). Figure 3 This is a schematic cross-sectional view showing the case where the front side 11a of the wafer 11 is attached to the front side of the support wafer. Additionally, the support wafer 17 attached to the wafer 11 has, for example, the same shape as the wafer 11.

[0058] The support wafer 17 can be made of monocrystalline silicon, just like the wafer 11. Additionally, multiple devices can be formed on the front side 17a of the support wafer 17. Furthermore, an adhesive 19, such as an acrylic adhesive or an epoxy adhesive, can be provided on the front side 17a of the support wafer 17.

[0059] Furthermore, in the bonding step (S1), with the back side 17b of the support wafer 17 supported, the front side 11a of the wafer 11 is pressed against the front side 17a of the support wafer 17 through the adhesive 19. Thus, a bonded wafer is formed in which the front side 11a of the wafer 11 is bonded to the front side 17a of the support wafer 17.

[0060] Next, a release layer is formed inside the wafer 11 using a laser processing device. Figure 4 This is a perspective view schematically illustrating an example of a laser processing apparatus for forming a release layer inside wafer 11. Additionally, Figure 4 The X-axis (left-right direction) and Y-axis (front-back direction) shown are perpendicular to each other on the horizontal plane. In addition, the Z-axis (up-down direction) is perpendicular to both the X-axis and Y-axis (vertical direction).

[0061] Figure 4 The laser processing apparatus 2 shown has a base 4 that supports all its components. A horizontal moving mechanism 6 is disposed on the upper surface of the 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.

[0062] A Y-axis moving plate 10 is connected to the upper surface of a pair of Y-axis guide rails 8 in a manner that allows it to slide along the pair of Y-axis guide rails 8. In addition, a lead 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 lead screw 12 is connected to the front end (one end) of the lead screw 12.

[0063] Furthermore, a nut portion (not shown) is provided on the surface of the lead screw shaft 12 with a helical groove to accommodate a large number of balls rolling on the surface of the rotating lead screw shaft 12, thus forming a ball screw. That is, when the lead screw shaft 12 rotates, a large number of balls circulate within the nut portion, and the nut portion moves along the Y-axis direction.

[0064] Furthermore, the nut is fixed to the lower surface of the Y-axis moving plate 10. Therefore, if the lead 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 on the upper surface of the Y-axis moving plate 10.

[0065] An X-axis moving plate 18 is connected to the upper surface of a pair of X-axis guide rails 16 in a manner that allows it to slide along the pair of X-axis guide rails 16. Additionally, a lead 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 lead screw 20 is connected to one end of the lead screw 20.

[0066] Furthermore, a nut portion (not shown) is provided on the surface of the lead screw shaft 20 with a helical groove to house a large number of balls rolling on the surface of the rotating lead screw shaft 20, thus forming a ball screw. That is, when the lead screw shaft 20 rotates, a large number of balls circulate within the nut portion, and the nut portion moves along the X-axis direction.

[0067] Furthermore, the nut is fixed to the lower surface of the X-axis moving plate 18. Therefore, if the lead screw 20 is rotated by the motor 22, the X-axis moving plate 18 and the nut move together along the X-axis direction.

[0068] 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. The holding stage 26 has, for example, a circular upper surface (holding surface) parallel to the X-axis and Y-axis directions, on which a perforated plate 26a is exposed.

[0069] Furthermore, a rotary drive source (not shown) such as an electric motor is connected to the lower part of the worktable base 24. When this rotary drive source is activated, the worktable 26 is kept rotating about a straight line passing through the center of the holding surface and parallel to the Z-axis direction as its rotation axis. Additionally, when the aforementioned horizontal movement mechanism 6 is activated, the worktable 26 is kept moving along the X-axis and / or Y-axis directions.

[0070] Furthermore, the perforated plate 26a is connected to a suction source (not shown) such as a vacuum pump via a flow path provided inside the holding stage 26. When this suction source operates, a negative pressure is generated in the space near the holding surface of the holding stage 26.

[0071] Additionally, a support structure 30 with sides substantially parallel to the Y-axis and Z-axis directions is provided in the area behind the base 4. A vertical moving mechanism 32 is disposed on the side of the support structure 30. Furthermore, the vertical moving mechanism 32 has a pair of Z-axis guide rails 34 fixed to the side of the support structure 30 and extending along the Z-axis direction.

[0072] A 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. In addition, a lead 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 lead screw is connected to the upper end (one end) of the lead screw.

[0073] Furthermore, a nut portion (not shown) is provided on the surface of the lead screw shaft with a helical groove to house a large number of balls rolling on the surface of the rotating lead screw shaft, thus forming a ball screw. That is, when the lead screw shaft rotates, a large number of balls circulate within the nut portion, and the nut portion moves along the Z-axis direction.

[0074] Furthermore, the nut is fixed to the back side of the Z-axis moving plate 36. Therefore, if the lead 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.

[0075] A support member 40 is fixed to the front side of the Z-axis moving plate 36. The support member 40 supports a portion of the laser beam irradiation unit 42. Figure 5 This is a schematic diagram illustrating the travel of the laser beam LB within the laser beam irradiation unit 42. Additionally, in Figure 5 In the diagram, some of the constituent elements of the laser beam irradiation unit 42 are shown using functional blocks.

[0076] The laser beam irradiation unit 42 has a laser oscillator 44 fixed to the base 4. The laser oscillator 44 has, for example, Nd:YAG as the laser medium, and emits a laser beam LB with a wavelength (for example, 1342 nm) that passes through the wafer 11. The laser beam LB is, for example, a pulsed laser beam with a frequency of 60 kHz.

[0077] Furthermore, the laser beam LB, after its output is adjusted in attenuator 46, is provided to spatial light modulator 48. In spatial light modulator 48, the laser beam LB is branched. For example, spatial light modulator 48 branches the laser beam LB, which has been adjusted in attenuator 46, so that the laser beam LB emitted from the illumination head 52 (described later) forms 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.

[0078] 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 converging the laser beam LB. The laser beam LB, converged by the focusing lens, is then emitted toward the holding surface side of the holding stage 26.

[0079] In addition, such as Figure 4As shown, the irradiation head 52 is disposed at the front end of the cylindrical housing 54. Furthermore, a support member 40 is fixed to the rear side of the housing 54. Additionally, an imaging unit 56 is fixed to the front side of the housing 54.

[0080] The imaging unit 56 includes, for example, a light source such as an LED (Light Emitting Diode); an objective lens; and imaging elements such as a CCD (Charge Coupled Device) image sensor or a CMOS image sensor.

[0081] Furthermore, when the aforementioned vertical movement mechanism 32 is activated, the laser beam irradiation unit 42 and the imaging unit 56 move along the Z-axis. Additionally, 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.

[0082] The touch panel 58 is composed of input devices such as capacitive or resistive touch sensors and display devices such as liquid crystal displays or organic EL (Electroluminescence) displays, and functions as a user interface.

[0083] When forming a release layer inside the wafer 11 using the laser processing apparatus 2, the wafer to be bonded is first 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. Then, a suction source communicating with the holding stage 26 is activated so that the wafer to be bonded is held by the holding stage 26.

[0084] Next, the imaging unit 56 captures an image of the back side 11b of the wafer 11 to which the wafer is attached. Then, referring to the image, the horizontal movement mechanism 6 is operated 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 peripheral area.

[0085] Additionally, referring to this image, the rotation drive source connected to the lower part of the worktable base 24 can be activated to keep the worktable 26 rotating so that the crystal orientation

[010] of the single crystal silicon constituting the wafer 11 is parallel to the X-axis direction and the crystal orientation

[001] is parallel to the Y-axis direction.

[0086] Next, a laser beam LB is irradiated into the annular first region of the wafer 11 that is inside the outer peripheral region, thereby forming a first release layer that serves as the starting point for separation between the region of the wafer 11 where multiple devices 15 are formed and the outer peripheral region (first release layer formation step: S2).

[0087] In the first stripping layer formation step (S2), while the laser beam LB is irradiating the annular first region of the wafer 11 that is inside the outer peripheral region, the holding stage 26 that holds the wafer 11 across the supporting wafer 17 is rotated. Figure 6 This is a partial cross-sectional side view schematically illustrating the situation where a laser beam LB is irradiated onto a rotating wafer 11.

[0088] Specifically, in the first stripping layer formation step (S2), a laser beam LB, branched in such a way as to form multiple (e.g., 2 to 10) focusing points with different positions (heights) in each Z-axis direction, is irradiated onto the wafer 11.

[0089] Of these multiple focusing points, for example, the lowest focusing point is positioned slightly higher than the front side 11a of the wafer 11, and the highest focusing point is positioned at the midpoint between the front side 11a and the back side 11b of the wafer 11. Furthermore, the multiple focusing points are arranged at equal intervals (e.g., 5μm to 15μm) along the Z-axis direction.

[0090] In this case, modified regions 21 with disordered crystal structure are formed inside the wafer 11, centered on multiple focal points. In addition, cracks 23 extend from multiple modified regions 21 in a manner that connects adjacent pairs of modified regions 21.

[0091] Thus, a release layer comprising multiple modified regions 21 and cracks 23 extending from the multiple modified regions 21 is formed inside the wafer 11. Next, while the laser beam LB is irradiating the wafer 11, a rotation drive source connected to the lower part of the stage base 24 is activated to rotate the holding stage 26 that holds the wafer in place by one revolution.

[0092] As a result, a release layer (first release layer) is formed between the region of the wafer 11 where the plurality of devices 15 are formed and the outer peripheral region. The first release layer has, for example, a cylindrical shape such that the lower bottom surface is located on the front side 11a of the wafer 11 and the upper bottom surface is located inside the wafer 11.

[0093] Next, a laser beam LB is irradiated into a second region of the wafer 11 that is inside the outer peripheral region, thereby forming a second release layer that serves as the separation starting point between the front side 11a and the back side 11b of the wafer 11 (second release layer formation step: S3). Figure 7 This is a flowchart illustrating an example of the second peel layer formation step (S3).

[0094] In the second release layer formation step (S3), a laser beam LB is first irradiated into a straight area along the crystal orientation

[010] of the monocrystalline silicon constituting the wafer 11 (laser beam irradiation step: S31). For example, when the wafer is held on the holding stage 26 with the crystal orientation

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

[0095] Figure 8 This is a partial cross-sectional side view schematically illustrating the situation where a laser beam LB is irradiated onto a wafer 11 moving along the X-axis. In this laser beam irradiation step (S31), for example, a laser beam LB branched in such a way that it forms multiple (e.g., 2 to 10) focusing points with different positions (coordinates) in the respective Y-axis directions is irradiated onto the wafer 11.

[0096] The plurality of focusing points are positioned, for example, at the same height as the uppermost modified region 21 among the plurality of modified regions 21 contained in the first exfoliation layer. In addition, the plurality of focusing points are arranged at equal intervals (e.g., 5 μm to 15 μm) according to their positions (coordinates) in the Y-axis direction.

[0097] In this case, similar to the first stripping layer formation step (S2), a plurality of modified regions 21 and cracks 23 extending from the plurality of modified regions 21 are formed inside the wafer 11. Then, while keeping the laser beam LB irradiating the wafer 11, the horizontal moving mechanism 6 is operated in such a way that the holding stage 26 holding the wafer is moved along the X-axis.

[0098] 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 with an absolute value of 10 or less, other than 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.

[0099] (101),(201),(301),(401),(501),(601),(701),(801),(901),( 10 001)

[0100]

[0101] Furthermore, the acute angle between the crystal plane (100) exposed on the front side 11a and the back side 11b of the wafer 11 and the crystal plane (k01) is 45° or less. Therefore, when 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 becomes larger than or equal to the vertical component.

[0102] Next, the holding stage 26 is moved along the crystal orientation

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

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

[0103] Next, the laser beam irradiation unit 42 and the horizontal movement mechanism 6 are operated in such a way that the peeling layer 25 is formed in a straight line parallel to the straight line area where the peeling layer 25 has already been formed. That is, the laser beam irradiation step (S31) is performed again. Figure 9 This is a schematic cross-sectional view of adjacent release layers 25 formed inside wafer 11 by the implementation of two laser beam irradiation steps (S31).

[0104] In this case, a release layer 25 (release layer 25-2) is formed inside the wafer 11, parallel to the release layer 25 (release layer 25-1) formed in the first laser beam irradiation step (S31) and away 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 to form the release layer 25 over the entire area of ​​the second region of the wafer 11 that is more inward than the outer peripheral region (from one end of the region in the Y-axis direction to the other end).

[0105] Furthermore, if a release layer 25 is formed over the entire area of ​​the second region inside the outer periphery of the wafer 11 (step (S33): Yes), then the second release layer formation step (S3) is completed. As a result, a release layer (second release layer) is formed between the front side 11a and the back side 11b of the wafer 11. This second release layer has, for example, a disk-shaped form along the upper bottom surface of a cylinder having a side surface along the aforementioned first release layer.

[0106] exist Figure 2 In the method shown, after the first stripping layer formation step (S2) and the second stripping layer formation step (S3) are performed, an external force is applied to the wafer 11, thereby separating the wafer 11 with the first stripping layer and the second stripping layer as the separation starting point (separation step: S4).

[0107] Figure 10 (A) and Figure 10 (B) is a partial cross-sectional side view schematically illustrating the separation of wafer 11. This separation step (S4) is, for example, in... Figure 10 (A) and Figure 10 The separation apparatus 60 shown in (B) is implemented. The separation apparatus 60 has a holding stage 62 for holding the bonded wafer containing the wafer 11 having the first release layer and the second release layer formed thereon.

[0108] The holding stage 62 has a circular upper surface (holding surface) on which a perforated plate (not shown) is exposed. Furthermore, the perforated plate is connected to a suction source (not shown) such as a vacuum pump via a flow path provided inside the holding stage 62. When the suction source is activated, a negative pressure is generated in the space near the holding surface of the holding stage 62.

[0109] Additionally, a separation unit 64 is provided above the holding worktable 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 the support member 66, and the separation unit 64 is raised and lowered by actuating this lifting mechanism.

[0110] 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. A plurality of grippers 70 are provided at approximately equal intervals along the circumference of the gripper base 68 on the lower side of its outer peripheral region. Each gripper 70 has a plate-shaped upright portion 70a extending downwards.

[0111] The upper end of the erected part 70a is connected to an actuator such as a cylinder built into the gripper base 68. By actuating the actuator, the gripper 70 moves radially along the gripper base 68. In addition, a plate-shaped claw part 70b is provided on the inner side of the lower end of the 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.

[0112] In the separation apparatus 60, the separation step (S4) is performed, for example, in the following order. Specifically, the bonding wafer is first placed on the holding stage 62 in such a way that the center of the back surface 17b of the support wafer 17, which contains the wafer 11 on which the first and second release layers are formed, is aligned with the center of the holding surface of the holding stage 62.

[0113] Next, the suction source communicating with the perforated plate exposed on the holding surface is activated to hold the bonded wafer by the holding stage 62. Then, the actuator is activated such that the plurality of gripping claws 70 are respectively positioned radially outward of the gripping claw base 68.

[0114] 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 reference). Figure 10 (A)).

[0115] Therefore, an upward external force, i.e., an external force along the thickness direction of the wafer 11, is applied to the outer peripheral region of the wafer 11. As a result, the cracks 23 contained in the first and second release layers extend further, separating the region of the wafer 11 in which the plurality of devices 15 are formed from the outer peripheral region and separating the front side 11a from the back side 11b (see reference). Figure 10 (B)

[0116] In the above wafer processing method, for 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, a laser beam LB is irradiated along the crystal direction

[010] , thereby forming a release layer (second release layer) that serves as the separation starting point between the front side 11a side and the back side 11b side of the wafer 11.

[0117] In this case, the cracks 23 extending from the modified region 21 are mostly along the crystal plane (k01) (k is an integer with an absolute value of 10 or less, excluding 0). Furthermore, the acute angle between the crystal plane (100) of the single-crystal silicon and the crystal plane (k01) is 45° or less. Therefore, in this wafer processing method, the component of the direction in which the cracks 23 extend that is parallel to the front side 11a and back side 11b of the wafer 11 (parallel component) becomes a component perpendicular to the wafer (vertical component) or greater.

[0118] Therefore, in this wafer processing method, the interval between adjacent modified regions 21 can be extended. As a result, the travel distance (indexing amount) in the indexing feed step (S32) can be extended, and the processing time (laser beam LB irradiation time) required to form the release layer 25, which serves as the separation starting point between the front side 11a and the back side 11b of the wafer 11, can be shortened.

[0119] Furthermore, in this wafer processing method, the crack 23 is less likely to extend from the release layer 25 toward the front side 11a of the wafer 11. As a result, the probability of device 15 breaking can be reduced when separating the front side 11a of the wafer 11 from the back side 11b.

[0120] 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 in the wafer 11, the front side 11a of the wafer 11 can be bonded to the front side 17a of the support wafer 17. That is, in the present invention, the bonding step (S1) can be performed after the first release layer forming step (S2) and the second release layer forming step (S3).

[0121] 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 be implemented using a laser processing apparatus equipped with a horizontal moving mechanism that moves the irradiation head 52 of the laser beam irradiation unit 42 along the X-axis and / or Y-axis directions, respectively.

[0122] That is, in this invention, as long as the holding stage 26 containing the wafer 11 and the irradiation head 52 of the laser beam irradiation unit 42 that emits the laser beam LB can move relative to each other along the X-axis and Y-axis directions respectively, there is no limitation on the structure used for movement.

[0123] Furthermore, in this invention, there is no limitation on the order of the first peel layer forming step (S2) and the second peel layer forming step (S3). That is, in this invention, the first peel layer forming step (S2) can be performed after the second peel layer forming step (S3).

[0124] However, when a disk-shaped second release layer is formed inside the wafer 11 in the second release layer formation step (S3), 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.

[0125] 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 allows for the reliable formation of a release layer (first release layer) that serves as the starting point for separation between the region of the wafer 11 where the plurality of devices 15 are formed and the peripheral region.

[0126] Alternatively, in this invention, it is preferable that the second region of the wafer 11 in which the second release layer is formed is located inside the first region in which the first release layer is formed. Therefore, even if the first release layer formation step (S2) is performed after the second release layer formation step (S3), the first release layer can be reliably formed.

[0127] Furthermore, in the first release layer formation step (S2) of the present invention, as long as a first release layer can be formed that functions as a separation starting point between the region of the wafer 11 where multiple devices 15 are formed and the peripheral region, the shape of the first release layer is not limited. For example, the first release layer may be the shape of a side surface of a cylinder located on the front side 11a of the wafer 11 with its lower bottom surface located on the back side 11b of the wafer 11.

[0128] That is, the first release layer can be formed to extend through the front side 11a and the back side 11b of the wafer 11. However, with the first release layer having such a shape, there is a concern that the outer peripheral area of ​​the wafer 11 may be scattered as scrap 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.

[0129] Alternatively, the first release layer can be shaped like the side of a frustum of a cone, with the lower bottom surface (first bottom surface) located on the front side 11a of the wafer 11 and the upper bottom surface (second bottom surface) having a diameter shorter than the lower bottom surface, located inside the wafer 11. Such a first release layer is formed, for example, by irradiating the wafer 11 with a laser beam LB in such a way that the formed focal point is closer to the outer peripheral region and thus closer to the front side 11a of the wafer 11.

[0130] Figure 11 This is a partial cross-sectional side view schematically illustrating the irradiation of a laser beam LB onto a rotating wafer 11 to form a first release layer of such shape. Specifically, in forming such a first release layer, the wafer 11 is first irradiated with a laser beam LB that forms multiple (e.g., eight) focal points in various directions of the wafer 11, both radially (perpendicular to the Z-axis) and in the thickness direction (Z-axis), with adjacent focal points offset by 10 μm inside the wafer 11.

[0131] In this case, multiple remodeling regions 21 are formed inside the wafer 11, centered on multiple light-focusing points, where the crystal structure of the material constituting the wafer 11 is disordered. That is, multiple remodeling regions 21 are formed that are arranged in a straight line along the radial direction of the wafer 11 when viewed from above, and the angle between the straight line and the front surface 11a of the wafer 11 is 45°.

[0132] Furthermore, the acute angle formed by the multiple modified regions 21 arranged in a straight line and the front surface 11a of the wafer 11 is not limited to 45°. That is, the laser beam LB can be irradiated onto the wafer 11 in such a way that multiple focal points are formed with different intervals in the radial direction and thickness direction between adjacent focal points of the wafer 11.

[0133] Furthermore, the cracks 23 extend from multiple modified regions 21 in a manner that connects adjacent pairs of modified regions 21. Thus, a release layer comprising multiple modified regions 21 and cracks 23 extending from multiple modified regions 21 is formed inside the wafer 11.

[0134] Next, while keeping the laser beam irradiation unit 42 in operation, the rotation drive source connected to the lower part of the worktable base 24 is activated so that the holding worktable 26 holding the wafer rotates one revolution.

[0135] As a result, a release layer (first release layer) is formed in the annular first region of the wafer 11 that is inside the outer peripheral region, such that a frustum-shaped side is formed along the lower bottom surface located on the front surface 11a side of the wafer 11 and the upper bottom surface located inside the wafer 11.

[0136] With such a first release layer formed, when the wafer 11 is separated in the separation apparatus 60, the probability that the side surface of the newly exposed region where multiple devices 15 are formed will come into contact with the inner surface of the outer peripheral region is reduced. Furthermore, in this case, the crack 23 is more likely to extend from the first release layer along the side surface of the frustum.

[0137] Therefore, in this case, the probability of crack 23 extending toward device 15 is also reduced, and damage to device 15 can be suppressed. Furthermore, with such a first release layer formed, it becomes easier to manufacture chips using the area near the outer periphery of the front side 11a of wafer 11. Therefore, in this case, the number of chips that can be manufactured from wafer 11 can be increased.

[0138] Furthermore, in the first stripping layer formation step (S2) of the present invention, 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, or alternatively, by a rotation drive source connected to the lower part of the worktable base 24. That is, the laser beam LB can be irradiated onto the wafer 11 not only by rotating the wafer 11, but also by changing the coordinates and height of the XY coordinate plane of the focusing point.

[0139] Furthermore, in the first release layer formation step (S2) of the present invention, multiple irradiations of laser beams LB with mutually concentrating points at the same or close positions can be performed. In this case, the size of the modified region 21 included in the release layer increases and the cracks 23 included in the release layer extend further. Therefore, in this case, the separation of the wafer 11 in the separation step (S4) becomes easier.

[0140] Furthermore, in the first release layer formation step (S2) of the present invention, the wafer 11 can be irradiated with a laser beam LB such that adjacent modified regions 21 are directly connected to each other without being connected via cracks 23. In this case, the shape of the release layer can be determined regardless of the shape of the cracks 23 extending from the modified regions 21, thus enabling stable processing of the wafer 11.

[0141] Furthermore, in the laser beam irradiation step (S31) of the second stripping 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 orientation

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

[001] .

[0142] Furthermore, when the wafer 11 is irradiated with a laser beam LB, the crack 23 tends to extend on the following crystal surfaces.

[0143] (110),(210),(310),(410),(510),(610),(710),(810),(910),( 1 010)

[0144]

[0145] Furthermore, in this invention, a laser beam LB can be irradiated onto a linear region that is slightly inclined from the crystal direction

[010] or the crystal direction

[001] when viewed from above. For this purpose, see [reference]. Figure 12 Please provide an explanation.

[0146] Figure 12 This is a graph showing the width (length in the direction perpendicular to the direction in which the linear region extends) of the release layer formed inside the wafer 11 when a laser beam LB is irradiated into a linear region along different crystal orientations. In addition, the horizontal axis of the graph shows the angle between the direction in which the linear region (reference region) perpendicular to the crystal orientation

[011] extends and the direction in which the linear region (measurement region) being measured extends when viewed from above.

[0147] That is, when the horizontal axis of the graph is 45°, a straight region along the crystal direction

[001] is taken as the measurement object. Similarly, when the horizontal axis of the graph is 135°, a straight region along the crystal direction

[010] is taken as the measurement object. In addition, the vertical axis of the graph shows the value when the width of the release layer formed in the measurement region by irradiating the measurement region with a laser beam LB is divided by the width of the release layer formed in the reference region by irradiating the reference region with a laser beam LB.

[0148] like Figure 12 As shown, the width of the release layer increases when the angle between the direction extending from the reference region and the direction extending from the measurement region is 40° to 50° or 130° to 140°. That is, the width of the release layer increases not only when a laser beam LB is irradiated on a straight region along the crystal direction

[001] or crystal direction

[010] , but also when a laser beam LB is irradiated on a straight region along a direction with an angle of 5° or less relative to these crystal directions.

[0149] 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 be irradiated on a straight area that is tilted less than 5° from the crystal direction

[001] or the crystal direction

[010] when viewed from above.

[0150] That is, in the laser beam irradiation step (S31), the laser beam can be applied parallel to and relative to the crystal orientation of the crystal plane (here, crystal plane (100)) exposed on the front side 11a and back side 11b of the wafer 11, which are specific crystal planes included in the crystal plane {100}. <100> A laser beam LB is irradiated in a straight region of a direction (first direction) in which the angle formed by the specific crystal orientation (here crystal orientation

[001] or crystal orientation

[010] ) is less than 5°.

[0151] Furthermore, when 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 forms a focal point through the irradiation of the laser beam LB, along a direction (second direction) that is parallel to and perpendicular to the first direction and to the crystal plane (here, crystal plane (100)) exposed on the front side 11a and back side 11b of the wafer 11, which is included in the specific crystal plane {100}.

[0152] In addition, in the second release layer formation step (S3) of the present invention, after the release layer 25 is formed on the entire area of ​​the second region (from the region on one end to the other end in the Y-axis direction) of the wafer 11 which is closer to the outer peripheral region (step S33: Yes), the laser beam irradiation step (S31) and the indexing feed step (S32) are repeated again.

[0153] That is, the second region where the release layer 25 has already been formed can be irradiated again with the same laser beam LB used to form the release layer 25. 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.

[0154] Furthermore, in the second release layer formation step (S3) of the present invention, the laser beam irradiation step (S31) can 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 already been formed can be irradiated again with the laser beam LB used to form the release layer 25. In this case, as described above, the separation of the wafer in the separation step (S4) becomes easier.

[0155] Furthermore, in the separation step (S4) of the present invention, the wafer 11 having the first and second release layers formed can be subjected to ultrasonic waves before separation. In this case, the cracks 23 contained in the first and second release layers extend, thus facilitating the separation of the wafer 11.

[0156] Furthermore, in the separation step (S4) of the present invention, a device other than the separation device 60 described above can 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 devices 15 are formed from the peripheral region, the front side 11a side and the back side 11b side of the wafer 11 can be separated.

[0157] The following is for reference Figures 13-15 An example of such a separation step (S4) will be illustrated. Figure 13 This is a schematic top view of a wafer 11 suitable for such a separation step (S4). In the outer peripheral region of the wafer 11, prior to the aforementioned bonding step (S1), a plurality of cuts 11d extending radially along the wafer 11 are formed.

[0158] The plurality of cuts 11d are formed at approximately equal intervals along the circumference of the wafer 11 in the area excluding the portion where the notch 13 is formed. Furthermore, the plurality of cuts 11d are formed such that the portion of the wafer 11 radially inward reaches the first release layer formed by the first release layer formation step (S2) described above.

[0159] Furthermore, the first release layer formed inside the wafer 11 has a shape resembling the side surface of a cylinder, with its lower bottom surface located on the front side 11a of the wafer 11 and its upper bottom surface located on the back side 11b of the wafer 11. That is, a first release layer is formed in the wafer 11 that extends through both the front side 11a and the back side 11b of the wafer 11.

[0160] Alternatively, the multiple cuts 11d can be formed, for example, by cutting the wafer 11 in a known cutting apparatus. Or, the multiple cuts 11d can be formed by irradiating the wafer 11 with a laser beam that generates laser ablation in a known laser processing apparatus.

[0161] Furthermore, in the outer peripheral region of wafer 11, multiple release layers extending radially along wafer 11 can be formed instead of multiple cuts 11d. These release layers can be formed, for example, by the same method used to form the first and second release layers described above.

[0162] Figure 14 (A) and Figure 14 (B) shows the respective... Figure 13 The diagram shows a partial cross-sectional side view of the wafer 11, where the region containing multiple devices 15 is separated from the peripheral region. This separation of the wafer 11 utilizes... Figure 14 (A) and Figure 14 The extension device 72 shown in (B) is used for this purpose.

[0163] The extension device 72 has a fixed cylindrical drum 74. A support unit 76 is provided around the drum 74. The support unit 76 has an annular support platform 78 arranged around the upper end of the drum 74. A plurality of clamps 80 are provided on the support platform 78 at approximately equal intervals along its circumference.

[0164] Furthermore, multiple cylinders are arranged at approximately equal intervals along the circumference of the support platform 78 below 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 extension device 72, by actuating the multiple cylinders, the support platform 78 and the multiple clamps 80 can be raised and lowered together with the piston rod 82.

[0165] In Figure 13 When the area where the multiple devices 15 are formed on the wafer 11 shown is separated from the outer peripheral area, an annular frame 29 is first attached to the peripheral area of ​​one side of the disk-shaped extension strip 27, and the back surface 11b of the wafer 11 is attached to the central area of ​​the extension strip 27. This forms a frame unit that integrates the wafer 11 and the supporting wafer 17, along with the annular frame 29.

[0166] Next, multiple cylinders are actuated such that the upper surface of the support platform 78 and the upper end of the drum 74 are on the same plane. Then, the annular frame 29 is placed on the support platform 78 via the extension belt 27. That is, the frame unit is placed on the support platform 78 with the support wafer 17 facing upwards.

[0167] Next, the annular frame 29 is fixed by multiple clamps 80 (see reference). Figure 14 (A) Next, multiple cylinders are actuated in a manner that lowers the annular frame 29, which is fixed by multiple clamps 80. As a result, the central region of the extension strip 27 is extended radially along the wafer 11 according to the amount by which the annular frame 29 is lowered.

[0168] At this time, a force is applied to the wafer 11 adhered to the extension tape 27 in a radially outward direction toward the wafer 11. As a result, the region of the wafer 11 in which the plurality of devices 15 are formed is separated from the peripheral region, with the first release layer as the separation starting point (see reference). Figure 14 (B)

[0169] Figure 15 (A) and Figure 15 (B) is a schematic representation of the following: Figure 14 (B) is a partial cross-sectional side view showing the separation of the front side 11a and the back side 11b of the wafer 11. The separation of the wafer 11 is achieved using... Figure 15 (A) and Figure 15 The separation device 84 shown in (B) is used for separation. This separation device 84 has a function for separating components... Figure 14 The holding stage 86 shown in (B) holds the wafer 11 in place.

[0170] The holding stage 86 has a circular upper surface (holding surface) on which a perforated plate (not shown) is exposed. Furthermore, the perforated plate is connected to a suction source (not shown) such as a vacuum pump via a flow path provided inside the holding stage 86. Therefore, when the suction source is activated, a negative pressure is generated in the space near the holding surface of the holding stage 86.

[0171] Additionally, a separation unit 88 is provided above the holding worktable 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 the support member 90, for example, and the separation unit 88 is raised and lowered by actuating this lifting mechanism.

[0172] 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 the suction plate 92, and these ports are connected to a suction source (not shown) such as a vacuum pump via flow paths provided inside the suction plate 92. Therefore, when the suction source operates, a negative pressure is generated in the space near the lower surface of the suction plate 92.

[0173] In Figure 14 When separating the front 11a side and the back 11b side of the wafer 11 shown in (B), the bonding wafer containing the wafer 11 is first removed from the extension tape 27. Then, 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.

[0174] Next, the suction source, which is connected to the perforated plate exposed on the holding surface, is activated by holding the wafer in place by the holding stage 86. Then, the lifting mechanism is activated to lower the separation unit 88 by bringing the lower surface of the suction plate 92 into contact with the back surface 11b of the wafer 11.

[0175] Next, the suction source, which is connected to the multiple suction ports, is activated to attract the back side 11b of the wafer 11 via the multiple suction ports formed on the suction plate 92. Then, the lifting mechanism is activated to raise the separation unit 88 by moving the suction plate 92 away from the holding table 86 (see reference). Figure 15 (A)).

[0176] At this time, for the wafer 11 attracted through the plurality of suction ports formed on the suction plate 92 on the back side 11b, an upward force is applied along the thickness direction of the wafer 11. As a result, the front side 11a and the back side 11b of the wafer 11 are separated with the second release layer as the separation starting point (see reference). Figure 15 (B)

[0177] In addition, the structure and method of the above embodiments can be appropriately modified and implemented as long as they do not depart from the scope of the purpose of the present invention.

Claims

1. A method for processing a single-crystal silicon wafer, wherein a single-crystal silicon wafer manufactured such that specific crystal planes included in crystal plane {100} are exposed on the front and back sides respectively, and multiple devices are formed on the front side and the outer peripheral region is chamfered, wherein after irradiating a laser beam having a wavelength that transmits through single-crystal silicon and whose focal point is located inside the single-crystal silicon wafer, thereby forming a release layer inside the single-crystal silicon wafer, the single-crystal silicon wafer is separated using the release layer as a separation starting point, wherein, The processing method for this single-crystal silicon wafer includes the following steps: In the bonding step, the front side of the monocrystalline silicon wafer is bonded to the front side of the support wafer; In the first stripping layer formation step, for the annular first region of the monocrystalline silicon wafer that is inside the outer peripheral region, the laser beam is irradiated from the back side of the monocrystalline silicon wafer, thereby forming a first stripping layer that serves as the starting point for separation between the region of the monocrystalline silicon wafer in which the plurality of devices are formed and the outer peripheral region. In the second release layer formation step, for a second region of the monocrystalline silicon wafer that is inside the outer peripheral region, the laser beam is irradiated from the back side of the monocrystalline silicon wafer, thereby forming a second release layer that serves as the separation starting point between the front side and the back side of the monocrystalline silicon wafer. as well as In the separation step, after the bonding step, the first release layer formation step, and the second release layer formation step, external force is applied to the monocrystalline silicon wafer, thereby separating the monocrystalline silicon wafer 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 the laser beam irradiation step and the indexing feed step, wherein, In this laser beam irradiation step, one side is parallel to the specific crystal plane and relative to the crystal orientation. <100> A first direction, containing specific crystal orientations with an angle of 5° or less, causes the single-crystal silicon wafer and the focusing point to move relative to each other, while irradiating the linear region along the first direction within the second region with the laser beam. In this indexing feed step, the position of the focal point formed by the laser beam irradiation inside the single-crystal silicon wafer is moved along a second direction that is parallel to the specific crystal plane and perpendicular to the first direction.

2. The method for processing single-crystal silicon wafers according to claim 1, wherein, The first peel layer formation step is performed before the second peel layer formation step.

3. The method for processing single-crystal silicon wafers according to claim 1, wherein, The second region is located inside the first region.

4. The method for processing a single-crystal silicon wafer according to 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.

5. The method for processing a single-crystal silicon wafer according to any one of claims 1 to 4, wherein, In the first release layer formation step, the laser beam is irradiated in such a way that the spotting point formed 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 along the side of the truncated cone. The first bottom surface of the truncated cone is located on the front side of the single crystal silicon wafer, and the second bottom surface, which is shorter in diameter than the first bottom surface, is located inside the single crystal silicon wafer.

Images