Wafer processing method and wafer processing apparatus

Abstract

The present application provides a wafer processing method and a wafer processing apparatus capable of efficiently processing a wafer into individual chips regardless of the kind of wafer or the kind of processing. According to the present application, a wafer processing method and a wafer processing apparatus are provided. The wafer processing method includes a holding step of holding a wafer (10) in a holding unit (4), a damage layer forming step of positioning a convergence point (P1) of a shock wave (PL3) at the wafer (10) held in the holding unit (4) to form a damage layer (S1) in a region to be divided, and a dividing step of dividing the wafer (10) into individual chips (12') with the damage layer (S1) as a starting point. The wafer processing apparatus includes a holding unit that holds a wafer, and a damage layer forming unit that positions a convergence point of a shock wave at the wafer held in the holding unit to form a damage layer in a region to be divided.

Description

Technical Field

[0001] The present invention relates to a wafer processing method and a wafer processing apparatus for dividing a wafer into individual chips. Background Technology

[0002] The wafer is divided by predetermined dicing lines to form multiple devices such as ICs, LSIs, and LEDs on its front side. The wafer is then divided into individual device chips by a laser processing device and used in electronic devices such as mobile phones and personal computers.

[0003] The laser processing apparatus comprises: a holding unit for holding a workpiece (wafer); a laser beam irradiation unit for irradiating a laser beam of a wavelength that is absorbent to the workpiece held by the holding unit; an X-axis feed unit for feeding the holding unit and the laser beam irradiation unit relative to each other in the X-axis direction; and a Y-axis feed unit for feeding the holding unit and the laser beam irradiation unit relative to each other in the Y-axis direction perpendicular to the X-axis direction. The laser processing apparatus positions a focal point on a predetermined slitting line of the wafer for irradiation, performs ablation processing, and forms slitting grooves on the predetermined slitting line to divide the wafer into individual device chips (see, for example, Patent Document 1).

[0004] Furthermore, the laser processing apparatus is configured to include: a holding unit that holds the workpiece (wafer); a laser beam irradiation unit that irradiates the workpiece held by the holding unit with a wavelength that is transparent to the workpiece; and a Y-axis feed unit that feeds the holding unit and the laser beam irradiation unit relative to each other in the Y-axis direction perpendicular to the X-axis direction. The laser processing apparatus positions the focal point of the laser beam inside the predetermined slitting line of the wafer and irradiates it, forming a modified layer inside the predetermined slitting line as the starting point of the slitting, thereby slitting the wafer into individual device chips (see, for example, Patent Document 2).

[0005] Patent Document 1: Japanese Patent Application Publication No. 10-305420

[0006] Patent Document 2: Japanese Patent Application Publication No. 2012-2604

[0007] However, the technology described in the aforementioned patent documents 1 and 2 has the following problem: the wavelength of the laser light irradiating the wafer must correspond to the type of wafer or the type of processing and have absorption or transmission properties, and a laser processing device corresponding to the type of wafer or the type of processing must be prepared, which is uneconomical. Summary of the Invention

[0008] The present invention was made in view of the above facts, and its main technical problem is to provide a wafer processing method and wafer processing apparatus that can efficiently process wafers into individual chips regardless of the type of wafer or the type of processing.

[0009] To address the aforementioned major technical challenges, according to the present invention, a wafer processing method is provided to divide a wafer into individual chips. The wafer processing method comprises the following steps: a holding step, in which the wafer is held in a holding unit; a destructive layer forming step, in which a destructive layer is formed in the region to be divided by positioning the convergence point of a shock wave on the wafer held by the holding unit; and a dividing step, in which the destructive layer is used as a starting point to divide the wafer into individual chips.

[0010] Furthermore, according to the present invention, a wafer processing apparatus is provided that divides a wafer into individual chips, wherein the wafer processing apparatus is configured to include: a holding unit that holds the wafer; and a destructive layer forming unit that positions the convergence point of a shock wave on the wafer held by the holding unit and forms a destructive layer in the region to be divided.

[0011] The destructive layer forming unit can be configured as a first laser beam irradiation unit that irradiates pulsed laser light. This first laser beam irradiation unit forms each pulse of laser light into a ring with a time difference for each wavelength. The ring-shaped pulsed laser light is irradiated onto the wafer, generating a shock wave in the area to be segmented, thus forming a convergence point. The first laser beam irradiation unit adjusts the time difference to set the position of the shock wave convergence point. Alternatively, the destructive layer forming unit can include: a liquid layer forming unit that forms a liquid layer on the upper surface of the wafer; a second laser beam irradiation unit that positions the focus point of the pulsed laser light on the liquid layer for irradiation; and an elliptical dome immersed in the liquid layer, configured such that the focus point of the pulsed laser light is positioned at a first focal point of the elliptical dome for irradiation, generating a shock wave in the liquid layer. The second focal point of the elliptical dome is positioned on the area of ​​the wafer to be segmented, thus making the second focal point the convergence point of the shock wave. Alternatively, the destructive layer forming unit may be configured to include: a liquid layer forming unit that forms a liquid layer on the upper surface of the wafer; a third laser beam irradiation unit that irradiates pulsed laser beams; and a shock wave generating unit that is immersed in the liquid layer and generates shock waves in the liquid layer by irradiation with pulsed laser beams, and forms a convergence point of the shock waves, wherein the convergence point formed by the shock wave generating unit is located in the region of the wafer to be delimited.

[0012] The wafer processing method of the present invention comprises the following steps: a holding step, in which the wafer is held in a holding unit; a destructive layer forming step, in which the convergence point of the shock wave is positioned on the wafer held by the holding unit and a destructive layer is formed in the area to be divided; and a dividing step, in which the wafer is divided into individual chips using the destructive layer as a starting point. Therefore, it is not necessary to select a laser beam with absorbent or transmissive properties corresponding to the raw material of the wafer, and therefore it is not necessary to prepare a laser processing apparatus corresponding to the type of wafer or the type of processing, and the wafer can be efficiently divided into individual chips.

[0013] Furthermore, the wafer processing apparatus of the present invention is configured to include: a holding unit for holding a wafer; and a destructive layer forming unit for positioning the convergence point of the shock wave on the wafer held by the holding unit and forming a destructive layer in the area to be divided. Therefore, it is not necessary to select a laser beam with absorbent or transmissive properties corresponding to the raw material of the wafer, and therefore it is not necessary to prepare a laser processing apparatus corresponding to the type of wafer or the type of processing, and the wafer can be efficiently divided into individual chips. Attached Figure Description

[0014] Figure 1 This is an overall perspective view of the wafer processing apparatus according to the first embodiment.

[0015] Figure 2 (a) and (b) are shown as being configured in Figure 1 A block diagram of the optical system of the first laser beam irradiation unit in the wafer processing apparatus shown.

[0016] Figure 3 This is a schematic diagram illustrating how a shock wave is generated by multiple ring lights irradiating a wafer, thereby forming a damaging layer inside the wafer.

[0017] Figure 4 This is a side view showing an implementation of the segmentation process.

[0018] Figure 5 This is an overall perspective view of the wafer processing apparatus according to the second and third embodiments.

[0019] Figure 6 It shows the configuration in Figure 5 A block diagram of the optical system of the second laser beam irradiation unit in the wafer processing apparatus shown.

[0020] Figure 7 (a) is a partially enlarged cross-sectional view showing the third concentrator of the third laser beam irradiation unit. Figure 7 (b) is a partially enlarged cross-sectional view showing the fourth concentrator in a modified example of the third laser beam irradiation unit.

[0021] Label Explanation

[0022] 2A, 2B: Wafer processing apparatus; 3: Base; 4: Holding unit; 21: Movable plate in the X-axis direction; 22: Movable plate in the Y-axis direction; 25: Chuck stage; 25a: Holding surface; 27: Fixture; 6: First laser beam irradiation unit; 61: Oscillator; 62: Wavelength differentiation delay unit; 64: Ring generation unit; 641, 642: Axial pyramidal lens; 643: Diffraction grating; 67: First condenser; 671: Condensing lens; 7: Imaging unit; 8A: Second laser beam irradiation unit; 81: Oscillator; 84a: Second condenser; 841a: Condensing lens; 842a: Glass plate; 843a: Laser beam guide section; 844a: Liquid inlet; 845a: Opening; 85a: Elliptical dome; 851a: Liquid layer; P2: First focal point; P3: Second focal point; 87: Opening section; 8B: Third laser beam irradiation unit 84b: Third concentrator; 841b: Concentrating lens; 842b: Glass plate; 85b: Dome component; 851b: Liquid layer; 852: Lower space; 844b: Liquid inlet; 8C: Laser beam irradiation unit (a variation of the third laser beam irradiation unit); 84c: Fourth concentrator; 844c: Liquid inlet; 85c: Hemisphere; 85d: Spherical surface; 85e: Flat surface; 851c: Liquid layer ; 10: Wafer; 10a: Front side; 10b: Back side; 12: Device; 12': Device chip; 14: Segmentation pre-line; 30: Moving unit; 31: X-axis feed unit; 32: Y-axis feed unit; 37: Frame; 37a: Vertical wall; 37b: Horizontal wall; 70: Segmentation device; 71: Frame holding component; 72: Fixture; 73: Expansion drum; 90: Liquid supply unit; 92: Piping. Detailed Implementation

[0023] Hereinafter, embodiments of the wafer processing method configured according to the present invention and the preferred wafer processing apparatus for implementing the wafer processing method will be described in detail with reference to the accompanying drawings.

[0024] exist Figure 1 The figure shows an overall perspective view of the wafer processing apparatus 2A as a first embodiment. The wafer processing apparatus 2A includes a base 3, a holding unit 4 for holding the workpiece, a first laser beam irradiation unit 6 provided as a destructive layer generation unit, an imaging unit 7, a moving unit 30 for moving the holding unit 4, and a control unit (not shown).

[0025] The holding unit 4 includes: a rectangular movable plate 21 in the X-axis direction, which is movably mounted on the base 3 in the X-axis direction as indicated by arrow X in the figure; a rectangular movable plate 22 in the Y-axis direction, which is movably mounted on the movable plate 21 in the X-axis direction as indicated by arrow Y in the figure; a cylindrical support column 23, which is fixed to the upper surface of the movable plate 22 in the Y-axis direction; and a rectangular cover plate 26, which is fixed to the upper end of the support column 23. A circular chuck worktable 25 extending upward through an elongated hole is provided on the cover plate 26. The chuck worktable 25 is configured to be rotated by a rotary drive unit (not shown). The holding surface 25a of the upper surface of the chuck worktable 25, defined by the X-axis and Y-axis coordinates, is formed of a porous material and is ventilated. It is connected to the suction unit (not shown) through a flow path passing through the interior of the support column 23. The chuck table 25 is also equipped with a clamp 27 for securing the annular frame F, which supports the workpiece by means of a protective strap T. Furthermore, the workpiece in this embodiment is, for example, a... Figure 1 The wafer 10 shown is formed on the front side 10a of a silicon substrate by dividing it by predetermined dividing lines 14, and a device 12 is formed thereon. The wafer 10 is attached to a protective strip T with the front side 10a facing upward and the back side 10b facing downward, and is held by a ring-shaped frame F by means of the protective strip T.

[0026] The moving unit 30 includes: an X-axis feed unit 31, which is mounted on the base 3 and feeds the holding unit 4 in the X-axis direction; and a Y-axis feed unit 32, which indexes the Y-axis movable plate 22 in the Y-axis direction. The X-axis feed unit 31 converts the rotational motion of the pulse motor 33 into linear motion via the ball screw 34 and transmits it to the X-axis movable plate 21, causing the X-axis movable plate 21 to move forward and backward along the guide rails 3a, 3a on the base 3 in the X-axis direction. The Y-axis feed unit 32 converts the rotational motion of the pulse motor 35 into linear motion via the ball screw 36 and transmits it to the Y-axis movable plate 22, causing the Y-axis movable plate 22 to move forward and backward along the guide rails 21a, 21a on the X-axis movable plate 21 in the Y-axis direction. Furthermore, although not shown in the diagram, position detection units are provided on the X-axis feed unit 31, the Y-axis feed unit 32, and the chuck table 25. These units accurately detect the X-axis coordinates, Y-axis coordinates, and circumferential rotational position of the chuck table 25, and send this position information to a control unit (not shown). Based on the instruction signal from the control unit using this position information, the rotation drive units of the X-axis feed unit 31, the Y-axis feed unit 32, and the chuck table 25 (not shown) are driven, enabling the chuck table 25 to be positioned at the desired location on the base 3.

[0027] like Figure 1As shown, a frame 37 is erected on the side of the moving unit 30. The frame 37 has a vertical wall portion 37a disposed on the base 3 and a horizontal wall portion 37b extending horizontally from the upper end of the vertical wall portion 37a. The optical system of the first laser beam irradiation unit 6 is housed inside the horizontal wall portion 37b of the frame 37, and a first condenser 67, which constitutes part of the optical system, is disposed on the lower surface of the front end of the horizontal wall portion 37b.

[0028] The imaging unit 7 is disposed on the lower front surface of the horizontal wall portion 37b and spaced apart from the first condenser 67 of the first laser beam irradiation unit 6 in the X-axis direction. The imaging unit 7 may include, as needed, a conventional imaging element (CCD) for capturing images using visible light, an infrared irradiation unit for irradiating the workpiece with infrared light, an optical system for capturing the infrared light irradiated by the infrared irradiation unit, and an imaging element (infrared CCD) that outputs an electrical signal corresponding to the infrared light captured by the optical system. The image captured by the imaging unit 7 is sent to the control unit (not shown) and appropriately displayed on the display unit (not shown).

[0029] The control unit is composed of a computer and includes: a central processing unit (CPU) that performs calculations according to the control program; a read-only memory (ROM) that stores the control program; and a read-write random access memory (RAM) that stores the calculation results. Furthermore, the control unit is electrically connected to the first laser beam irradiation unit 6, the imaging unit 7, and the moving unit 30, and controls the actions of each unit.

[0030] Reference Figure 2 (a) The optical system of the first laser beam irradiation unit 6, which is built into the horizontal wall portion 37b of the wafer processing apparatus 2A, will be described.

[0031] Figure 2The first laser beam irradiation unit 6 shown in (a) includes: an oscillator 61 that oscillates a wide-band wavelength (e.g., 355nm to 1064nm) pulsed laser beam PL0; a wavelength differentiation delay unit 62 that outputs pulsed laser beam PL1 with a time difference for each pulse of oscillation by the oscillator 61 according to each wavelength; a collimating lens 63 that makes the pulsed laser beam PL1 parallel light; a ring generation unit 64 that generates the pulsed laser beam PL1 into a ring light and generates pulsed laser beam PL2 by splitting the small ring light into a large ring light according to each wavelength; a reflector 66 that modifies the optical path of the pulsed laser beam PL2; and a first concentrator 67 that includes a concentrating lens 671 that focuses the pulsed laser beam PL2 onto the upper surface 10a of the wafer 10 held by the chuck stage 25, i.e., the front surface 10a, for irradiation by the X-axis coordinate and the Y-axis coordinate.

[0032] The wavelength differentiation delay unit 62 of the guided pulsed laser beam PL0 can be implemented, for example, by using an optical fiber that generates wavelength dispersion. More specifically, it can be implemented, for example, by forming a diffraction grating in the optical fiber (not shown) contained within the wavelength differentiation delay unit 62, such that the reflection position is different for each wavelength, for example, configured to make the reflection distance of long wavelength light short and the reflection distance of short wavelength light long. Thus, by setting... Figure 2 The optical fiber 621 on the output side of the wavelength differentiation delay unit 62 shown in (a) causes each pulse to have a predetermined time difference in order of wavelength from longest to shortest, for example generating a pulsed laser beam PL1 including red light PL1a, yellow light PL1b, green light PL1c, and blue light PL1d with time differences. Furthermore, in this embodiment, for ease of explanation, an example is described where the pulsed laser beam PL0 is split into red light PL1a, yellow light PL1b, green light PL1c, and blue light PL1d corresponding to four wavelength regions; however, in practice, the splitting is performed corresponding to 10 to 20 wavelength regions.

[0033] The ring generation unit 64 is implemented, for example, using an axial pyramidal lens body, which has a pair of axial pyramidal lenses 641 and 642 and a diffraction grating 643 symmetrical in the radial direction in a dollop shape. The pulsed laser beam PL1 is formed into a ring shape by passing through the pair of axial pyramidal lenses 641 and 642, and further passes through the diffraction grating 643 to generate a pulsed laser beam PL2, which is obtained by splitting the small ring beam into a large ring beam according to each wavelength. By adjusting the spacing between the pair of axial pyramidal lenses 641 and 642, the size of the ring beam constituting the pulsed laser beam PL2 can be adjusted. Furthermore, in this embodiment, the example of using an axial pyramidal lens body is shown as a component for splitting the pulsed laser beam PL1 into a large ring beam according to each wavelength; however, the invention is not limited to this, and diffractive optical elements (DEOs) can be used for example.

[0034] The pulsed laser beam PL2 generated by the ring generation unit 64 has its optical path altered by the reflector 66 and is guided to the first concentrator 67, which includes a focusing lens 671, to irradiate the wafer 10. Additionally, in Figure 2 In the description of (a), the protective strip T and frame F that hold the wafer 10 are omitted.

[0035] exist Figure 3 The diagram below illustrates how shock waves PL3 are generated by the ring lights PL2a to PL2d constituting the pulsed laser beam PL2 and converged to a predetermined convergence point (position P1) inside the wafer 10. As shown, the ring lights PL2a to PL2d reach the front surface 10a of the wafer 10, thereby generating shock waves PL3 that propagate within the wafer 10 from each point of arrival. By appropriately setting the time differences t1 to t3 when each ring light PL2a to PL2d reaches the front surface 10a of the wafer 10, the desired position P1 in the thickness direction of the wafer 10 at the center C of each ring light PL2a to PL2d illuminating the front surface 10a of the wafer 10 can be used as the convergence point to converge the shock waves PL3. In this embodiment, the position P1 is set at a depth Pz in the Z-axis direction with the front surface 10a of the wafer 10 as a reference. With position P1 as the convergence point, the appropriate order of setting the time differences t1 to t3 is as follows.

[0036] The diameters of the ring lights PL2a to PL2d illuminating the front surface 10a of the wafer 10 are values ​​set by the diffraction grating 643 included in the ring generation unit 64, for example, as shown in the figure. Figure 3As shown, a1 to a4 are set. Furthermore, when the Z-axis coordinate (depth) from the center C of the ring lights PL2a to PL2d along the thickness direction of the wafer 10 to the position P1 where the operator wants the shock waves PL3 generated by each ring light PL2a to PL2d to converge is set to Pz, the distances H1 to H4 from the point reached by each ring light PL2a to PL2d on the front surface 10a of the wafer 10 to that position P1 are calculated using the following formulas.

[0037] H1=(a1 2 +Pz 2 ) 1 / 2

[0038] H2=(a2 2 +Pz 2 ) 1 / 2

[0039] H3=(a3 2 +Pz 2 ) 1 / 2

[0040] H4=(a4 2 +Pz 2 ) 1 / 2

[0041] Here, as described above, when the ring lights PL2a to PL2d arrive at the front surface 10a of the wafer 10 with time differences t1 to t3, generating a shock wave PL3 that propagates inside the wafer 10, in order to converge the shock wave PL3 to position P1, a time difference t1 to t3 satisfying the following formula can be set. Furthermore, V is the velocity (m / s) of the shock wave PL3 propagating inside the wafer 10, and this velocity is determined by the material of the wafer 10.

[0042] (H1-H2) / V=t1

[0043] (H2-H3) / V=t2

[0044] (H3-H4) / V=t3

[0045] The aforementioned time difference t1 to t3 can be set by the aforementioned wavelength differentiation delay unit 62. In the aforementioned wavelength differentiation delay unit 62, the position of the diffraction grating (not shown) arranged in the optical fiber constituting the wavelength differentiation delay unit 62 in accordance with the manner of generating the aforementioned time difference t1 to t3 is set.

[0046] The ring light PL2a to PL2d is irradiated onto the front surface 10a of the wafer 10 according to the time difference t1 to t3 that meets the above conditions. As a result, the shock wave PL3 generated by the ring light PL2a to PL2d and propagating in the wafer 10 converges to position P1 and generates a strong impact.

[0047] Furthermore, the laser irradiation conditions for activating the first laser beam irradiation unit 6 described above are as follows. By appropriately adjusting the average output of the pulsed laser beam PL0 irradiated from the oscillator 61, the shock wave PL3 can be converged at position P1 inside the wafer 10 as a convergence point, causing damage at position P1.

[0048]

[0049] The wafer processing apparatus 2A of the first embodiment has a structure roughly as described above, as will be referred to below. Figures 1 to 3 The wafer processing method implemented by the wafer processing apparatus 2A and the way in which the first laser beam irradiation unit 6 of the wafer processing apparatus 2A functions as a destructive layer forming unit will be described.

[0050] When a destructive layer is to be formed at a predetermined depth (Pz) P1 from the front surface 10a in the area to be divided (division predetermined line 14) of the wafer 10, the protective tape T on which the wafer 10 is attached is first placed on the holding surface 25a of the chuck stage 25 of the holding unit 4. The suction unit (not shown) is activated to perform suction and holding, and the frame F holding the wafer 10 is fixed by the clamp 27 (holding process). If this holding process is performed, the destructive layer formation process is then performed.

[0051] During the destructive layer formation process, the moving unit 30 is first activated to position the wafer 10 below the imaging unit 7. Next, the imaging unit 7 takes an image of the front side 10a of the wafer 10, thereby detecting the position of the area to be divided, i.e., the division predetermined line 14 (alignment process).

[0052] If the alignment process is performed, the wafer 10 is moved below the first condenser 67, and the pre-division line 14 obtained through the alignment process is aligned along the X-axis direction, and the position to be processed in the pre-division line 14 is positioned directly below the first condenser 67.

[0053] like Figure 3 As shown, in the wafer processing apparatus 2A of this embodiment, shock waves PL3 are generated inside the wafer 10 by the ring light PL2a to PL2d of each wavelength converged by the first concentrator 67 including the concentrator lens 671. The shock waves PL3 propagating inside the wafer 10 are converged to a position P1 at a predetermined depth Pz when viewed from the front surface 10a of the wafer 10 in the Z-axis direction by appropriately setting time differences t1 to t3 as described above. At the same time, the moving unit 30 is activated to perform processing feed of the chuck stage 25 in the X-axis direction, so that the shock waves PL3 are sequentially converged to the predetermined depth Pz position, as described above. Figure 2 As shown in (a), a destructive layer S1 is formed inside the wafer 10. As a result, the destructive layer S1 is formed inside the predetermined dicing line 14 along the predetermined dicing line 14. If the destructive layer S1 is formed inside the predetermined dicing line 14, the Y-axis feed unit of the moving unit 30 is activated to index the wafer 10, positioning the adjacent unprocessed predetermined dicing line 14 directly below the first condenser 67. The aforementioned ring light PL2a to PL2d is positioned on the predetermined dicing line 14 for irradiation, and the X-axis feed unit 31 is activated to form the destructive layer S1 inside the predetermined dicing line 14. If the destructive layer S1 is thus formed inside all predetermined dicing lines 14 along the predetermined direction, a rotation drive unit (not shown) that rotates the chuck stage 25 is controlled to rotate the chuck stage 25 by 90 degrees, forming the destructive layer S1 inside all predetermined dicing lines 14 formed in a direction perpendicular to the predetermined dicing line 14 where the destructive layer S1 was previously formed. Through the above, a destructive layer S1 is formed along the predetermined dividing line 14, which is the starting point when the wafer 10 is divided into individual chips, thus completing the destructive layer formation process.

[0054] If the destructive layer formation process is completed as described above, a dicing process is performed to divide the wafer 10 into individual device chips 12', starting from the destructive layer S1. This dicing process can utilize known cells, for example, using... Figure 4 The dividing device 70 shown is used to implement this.

[0055] The wafer 10, in which the destructive layer S1 has been formed inside the dicing predetermined line 14 through the destructive layer formation process as described above, is transported to... Figure 4 The dividing device 70 shown includes: an annular frame holding member 71 configured to be movable; a clamp 72 that holds the frame F by placing it on its upper surface; an expansion drum 73 formed in a cylindrical shape with at least an opening at the top for expanding the spacing between the devices 12 of the wafer 10 mounted on the frame F held by the clamp 72; and a support unit 74 consisting of a plurality of cylinders 74a arranged around the expansion drum 73 and piston rods 74b extending from the cylinders 74a.

[0056] The expansion drum 73 is set to be smaller than the inner diameter of the frame F and larger than the outer diameter of the chip 10 attached to the protective strip T mounted on the frame F. Here, as... Figure 4 As shown, the dividing device 70 can raise and lower the frame holding member 71 to a position that is approximately at the same height as the upper surface of the expansion drum 73 (shown by dashed lines) and a position where the upper end of the expansion drum 73 is relatively higher than the upper end of the frame holding member 71 (shown by solid lines).

[0057] When the frame holding member 71 is lowered as described above, causing the upper end of the expansion drum 73 to change from the position shown by the dashed line to a higher position shown by the solid line, the protective strip T mounted on the frame F is expanded by the upper edge of the expansion drum 73. Here, the wafer 10 has a destructive layer S1 as the starting point of the dicing along the predetermined dicing line 14 through the above-described destructive layer formation process. The expansion of the protective strip T exerts a radial tensile force (external force) on the wafer 10, thereby... Figure 4 As shown, the wafer 10 is divided into device chips 12'. If the wafer 10 is divided into individual device chips 12' in this way, they are picked up by a suitable pickup device (not shown).

[0058] According to the above-described embodiment, a ring-shaped pulsed laser beam PL2 can be irradiated onto the pre-defined dividing line 14 of the front side 10a of the wafer 10, generating a shock wave PL3 and causing the shock wave PL3 to converge at a predetermined position P1 to generate a destructive layer S1 inside the pre-defined dividing line 14. Regarding the laser beam irradiated at this time, it is not necessary to select a wavelength with absorption or transmission corresponding to the raw material of the wafer 10. It can be a broadband wavelength laser beam set in any range. Therefore, it is not necessary to prepare a laser processing apparatus corresponding to the type of wafer or the type of processing.

[0059] Furthermore, the present invention is not limited to the first embodiment described above. For example, it may also be as follows: Figure 2 As shown in (b), the convergence point of the shock wave PL3' generated by irradiating a pulsed laser beam PL2, which is configured to contain ring lights PL2a to PL2d of each wavelength, is set at a position P1' defined by a depth Pz' near the front surface 10a of the wafer 10. In this way, a destructive layer S2, which serves as the starting point of the slitting, can be formed, similar to an ablation process performed by irradiating the front surface 10a of the wafer 10 along the predetermined slitting line 14 with a laser beam of an absorptive wavelength.

[0060] This invention is not limited to the first embodiment described above. See also... Figures 5 to 7 The second and third embodiments of a wafer processing apparatus capable of implementing the wafer processing method of the present invention will be described.

[0061] exist Figure 5 The image shows an overall perspective view of the wafer processing apparatus 2B according to the second and third embodiments. The wafer processing apparatus 2B is shown relative to a reference slab. Figure 1 and Figure 2 The difference in the described wafer processing apparatus 2A is that, instead of the first laser beam irradiation unit 6 which is provided as a destructive layer formation unit, other laser beam irradiation units 8A to 8C are provided, which also function as destructive layer formation units. Furthermore, in the following description, the markings indicating the difference between... and... Figure 1 , Figure 2Detailed description of the same structures with the same reference numerals as the first embodiment shown.

[0062] exist Figure 5 In the wafer processing apparatus 2B shown, a liquid supply unit 90 for supplying liquid L (e.g., water) to the wafer 10, which is the workpiece, is disposed within or near the wafer processing apparatus 2B. The liquid supply unit 90 includes: a container for storing liquid L; and a pressure pump for ejecting liquid L from the container to the outside (both omitted from the illustration). The liquid L ejected from the liquid supply unit 90 is supplied via piping 92 to the concentrators 84a-84c of the other laser beam irradiation units 8A-8C constituting the destructive layer forming unit of this embodiment. The optical systems of the other laser beam irradiation units 8A-8C are housed inside the horizontal wall 37b of the frame 37 disposed on the base 3. (See reference...) Figure 6 The optical system of the second laser beam irradiation unit 8A provided in the second embodiment will be described.

[0063] like Figure 6 As shown, the second laser beam irradiation unit 8A includes: an oscillator 81 that oscillates a broadband wavelength pulsed laser beam PL0; a collimating lens 82 that makes the pulsed laser beam PL0 parallel; a reflector 83 that modifies the optical path of the pulsed laser beam PL0, which has become parallel light after passing through the collimating lens 82, as needed; and a second condenser 84a that guides the pulsed laser beam PL0 reflected by the reflector 83. Additionally, although not shown in the figure, this optical system also includes an attenuator for adjusting the output of the pulsed laser beam PL0 oscillated from the oscillator 81.

[0064] like Figure 6 As shown, viewed from the side where the pulsed laser beam PL0 is introduced (the upper side of the figure), a focusing lens 841a, a glass plate 842a, a laser beam guide section 843a, and an elliptical dome 85a are arranged inside the second concentrator 84a. The elliptical dome 85a is formed by a portion of an ellipsoid whose longitudinal section is composed of ellipses, and the elliptical dome 85a and the laser beam guide section 843a are connected via an opening 845a. A liquid inlet 844a, which together with the liquid supply unit 90 constitutes a liquid layer forming unit, is connected from the side to the laser beam guide section 843a. The glass plate 842a allows the pulsed laser beam PL0 to pass through and vertically divides the interior of the second concentrator 84a.

[0065] The elliptical dome 85a formed within the second concentrator 84a is composed of a portion of an ellipsoid, as described above. The ellipse forming this ellipsoid is defined by a first focal point P2 and a second focal point P3, which serve as references to the ellipse. The first focal point P2 is located on the side of the laser beam guide portion 843a within the elliptical dome 85a. Furthermore, the second focal point P3 is located below the lower end 86a of the second concentrator 84a and on the outer side of the elliptical dome 85a.

[0066] When implementing the wafer processing method of this embodiment using the second laser beam irradiation unit 8A described above, the holding process described above is first performed to hold the wafer 10 on the chuck stage 25. Next, the wafer 10 held by the chuck stage 25 is moved to a position directly below the imaging unit 7, and the wafer 10 is photographed by the imaging unit 7 to perform an alignment process. If this alignment process is performed, the chuck stage 25 is rotated and moved by the movement unit 30 according to the position and direction of the pre-defined dividing line 14 obtained from the image of the wafer 10, using a control unit (not shown), to adjust the pre-defined dividing line 14 of the wafer 10 to be oriented along the X-axis direction, and the position where processing is to begin in the pre-defined dividing line 14 is positioned directly below the second condenser 84a of the second laser beam irradiation unit 8A.

[0067] If the wafer 10 is positioned directly below the second concentrator 84a of the second laser beam irradiation unit 8A, the height adjustment unit (not shown) is activated to adjust the height of the second laser beam irradiation unit 8A, and the second focal point P3 of the elliptical dome 85a is positioned inside the predetermined dividing line 14 of the wafer 10 and at a predetermined depth (Pz) from the front surface 10a of the wafer 10 at which the destructive layer S3 is to be generated.

[0068] Next, the liquid supply unit 90 is activated to introduce liquid L through the liquid inlet 844a via the piping 92. The liquid L introduced from the liquid inlet 844a is guided to the elliptical dome 85a via the laser beam guide section 843a, and discharged to the outside through the gap between the lower end 86a of the second concentrator 84a and the front surface 10a of the wafer 10. In this way, the liquid L introduced into the second concentrator 84a forms a liquid layer 851a on the wafer 10, resulting in the elliptical dome 85a being immersed in the liquid layer 851a.

[0069] As described above, the second focus P3 of the ellipse forming the elliptical dome 85a is positioned below the front surface 10a of the wafer 10 at a distance Pz. The moving unit 30 is activated to move the wafer 10 along the predetermined dividing line 14 arranged in the X-axis direction. Simultaneously, the second laser beam irradiation unit 8A is activated to irradiate a pulsed laser beam PL0. Here, as... Figure 6As shown, the focusing lens 841a is configured to converge the pulsed laser beam PL0 to a first focal point P2 located within the liquid layer 851a. When the laser beam PL0 converges to the first focal point P2, a shock wave PL3a is generated at the first focal point P2. The shock wave PL3a generated at the first focal point P2 propagates in the liquid L constituting the liquid layer 851a and is reflected at various locations on the inner wall of the elliptical dome 85a. The shock wave PL3a reflected at various locations on the inner wall of the elliptical dome 85a reaches the front surface 10a of the wafer 10, further propagating within the wafer 10, and converges at a second focal point P3 located at a depth Pz along the Z-axis direction from the front surface 10a of the wafer 10, forming a destructive layer S3 along the interior of the predetermined dividing line 14 located along the X-axis direction.

[0070] If a destructive layer S3 is formed in the X-axis direction at a predetermined depth (Pz) as described above, the moving unit 30 is activated to appropriately index the chuck stage 25 in the Y-axis direction, positioning the second focus P3 inside the predetermined dicing line 14 adjacent to the previously formed destructive layer S3. The chuck stage 25 is then moved along the X-axis direction to further form the destructive layer S3. By repeating this process, a destructive layer S3 is formed inside all predetermined dicing lines 14 formed along the predetermined direction of the wafer 10. If a destructive layer S3 is formed inside all predetermined dicing lines 14 along the predetermined direction, a rotary drive unit (not shown) is controlled to rotate the chuck stage 25 90 degrees, forming a destructive layer S3 inside all predetermined dicing lines 14 in a direction perpendicular to the previously formed destructive layer S3. Through the above, a destructive layer S3 is formed along the predetermined dicing lines 14, serving as the starting point for dividing the wafer 10 into individual chips, thus completing the destructive layer formation process (destructive layer formation process). If the destructive layer formation process is performed, the wafer 10 can be divided into individual device chips 12' by using the aforementioned dividing device 70 to perform the dividing process.

[0071] Furthermore, in the destructive layer formation process of this embodiment, the laser irradiation conditions implemented by the second laser beam irradiation unit 8A are set as follows, for example.

[0072]

[0073] Through the above-described embodiments, a shock wave PL3a can also be generated in the wafer 10 and propagated inside the wafer 10. The shock wave PL3a is then focused at a second focal point P3 set at a predetermined depth Pz along the predetermined dividing line 14 of the wafer 10 to generate a destructive layer S3. Regarding the laser light irradiated at this time, it is not necessary to select a wavelength with absorption or transmission corresponding to the raw material of the wafer 10. It can be a broadband wavelength laser light set in any range. Therefore, it is not necessary to prepare a laser processing apparatus corresponding to the type of wafer or the type of processing.

[0074] According to the present invention, various modifications are provided, not limited to the second embodiment described above. (See also...) Figure 7 The third embodiment and its variations will be described.

[0075] exist Figure 7 The third laser beam irradiation unit 8B used in the third embodiment shown in (a) is only used in place of the third laser beam irradiation unit 8B used in the third embodiment shown in (a) in order to replace ... Figure 5 and Figure 6 The second embodiment of the wafer processing apparatus 2B, as described above, differs in that the second laser beam irradiation unit 8A is equipped with a third concentrator 84b instead of a second concentrator 84a. Therefore, in Figure 7 In (a), only the structure of the third concentrator 84b of the third laser beam irradiation unit 8B is shown, and other structures are omitted.

[0076] like Figure 7 As shown in (a), the third concentrator 84b, viewed from above, has a concentrating lens 841b and a glass plate 842b inside. A dome component 85b, formed of a hollow hemisphere and functioning as the shock wave generating unit of the present invention, is disposed in the lower space 852 divided by the glass plate 842b. A liquid inlet 844b, forming a liquid layer forming unit together with the liquid supply unit 90, is formed on the side of the lower space 852. A pipe 92 for introducing liquid L from the liquid supply unit 90 is connected to the liquid inlet 844b. An opening H is formed at the apex of the dome component 85b, connecting the upper side of the dome component 85b to the hollow interior. Furthermore, the dome component 85b is formed, for example, of a rigid material that does not transmit pulsed laser light PL0, such as metal or glass. The function of the third concentrator 84b thus formed will be explained below.

[0077] When implementing the wafer processing method of this embodiment using the third laser beam irradiation unit 8B described above, after performing the holding and alignment processes, the chuck stage 25 is rotated by the moving unit 30 to adjust the direction of the pre-defined dicing line 14 of the wafer 10 to be aligned along the X-axis, and the processing start position of the pre-defined dicing line 14 is positioned directly below the third condenser 84b of the third laser beam irradiation unit 8B. When the processing start position of the pre-defined dicing line 14 is positioned directly below the third condenser 84b of the third laser beam irradiation unit 8B, a height adjustment unit (not shown) is activated to adjust the height of the third laser beam irradiation unit 8B to a predetermined height. This predetermined height will be described later.

[0078] If the predetermined dividing line 14 of the wafer 10 is positioned directly below the third concentrator 84b and the third laser beam irradiation unit 8B is positioned at a predetermined height as described above, the liquid supply unit 90 is activated, allowing liquid L to be introduced into the lower space 852 via the pipe 92 and the liquid inlet 844b. The liquid L introduced from the liquid inlet 844b fills the lower space 852 within the third concentrator 84b and is introduced into the hollow region inside the dome member 85b via the opening H formed at the apex of the dome member 85b, forming a liquid layer 851b. The liquid L forming the liquid layer 851b is discharged to the outside through the gap between the lower end 86b of the third concentrator 84b and the front surface 10a of the wafer 10. Thus, by introducing liquid L into the lower space 852 of the third concentrator 84b, a liquid layer 851b is formed on the wafer 10, resulting in the dome member 85b being immersed in the liquid layer 851b.

[0079] If the third laser beam irradiation unit 8B, which includes the third concentrator 84b having the dome component 85b described above, is positioned at a predetermined height relative to the predetermined dividing line 14 of the wafer 10, the third laser beam irradiation unit 8B is operated while the wafer 10 is moved in the X-axis direction by the moving unit 30, for example, irradiating the pulsed laser beam PL0 under the same laser irradiation conditions as in the second embodiment described above. Figure 7As shown in (a), the pulsed laser beam PL0 is guided to the focusing lens 841b of the third concentrator 84b for focusing, and then irradiates the dome component 85b via the glass plate 842b. The dome component 85b, as described above, does not transmit the pulsed laser beam PL0 and is formed of a rigid material (metal, glass, etc.) that transmits vibrations. The pulsed laser beam PL0 irradiates the upper surface of the dome component 85b, thereby generating a shock wave PL3b in the liquid layer 851b. The shock wave PL3b propagates in the liquid layer 851b formed inside the dome component 85b and reaches the front surface 10a of the wafer 10, further propagating inside the wafer 10. In this embodiment, as described above, the height of the third laser beam irradiation unit 8B is adjusted to a predetermined height, which is the predetermined height at which the position P4 where the shock wave PL3b generated by the dome component 85b converges inside the wafer 10 to form the destructive layer S4 reaches a desired depth Pz.

[0080] As described above, through Figure 7 The third laser beam irradiation unit 8B shown in (a) can also cause the shock wave PL3a to converge along the predetermined dividing line 14 of the wafer 10 at a position P4 set at a predetermined depth Pz to generate a destructive layer S4. It is not necessary to select a laser beam with absorbency or transmittance corresponding to the raw material of the wafer 10, and it is not necessary to prepare a laser processing device corresponding to the type of wafer or the type of processing.

[0081] Additionally, refer to Figure 7 (b) will describe a modified example of the laser beam irradiation unit 8C provided in the third embodiment, which is a third laser beam irradiation unit 8B. The laser beam irradiation unit 8C is only used in place of the laser beam irradiation unit 8B provided in the third embodiment. Figure 7 The third laser beam irradiation unit 8B described in (a) differs in that it is equipped with a fourth concentrator 84c, while the third concentrator 84b is provided. Therefore, in Figure 7 In (b), only the fourth concentrator 84c is shown, and other structures are omitted.

[0082] like Figure 7As shown in (b), the fourth condenser 84c, viewed from above, is equipped with a condensing lens 841c and a solid hemisphere 85c that functions as a shock wave generating unit of the present invention. A liquid inlet 844c, which together with the liquid supply unit 90 forms a liquid layer forming unit, is formed in the wall portion 88 constituting the fourth condenser 84c. A passage 89 is formed inside the wall portion 88 to guide the liquid L introduced from the liquid inlet 844c to the lower end 86c side of the fourth condenser 84c. A pipe 92 for introducing liquid L from the liquid supply unit 90 is connected to the liquid inlet 844c. The hemisphere 85c is disposed on the lower side of the fourth condenser 84c, with the spherical surface 85d of the hemisphere 85c facing the upper side where the condensing lens 841c is disposed, and the flat surface 85e is coplanar with the lower end 86c of the fourth condenser 84c. The hemisphere 85c is formed of a rigid component that does not transmit the pulsed laser beam PL0, such as metal or glass. The lower end 86c of the fourth concentrator 84c is closed by the hemisphere 85c. The function of the fourth concentrator 84c thus formed will be explained below.

[0083] When implementing the wafer processing method of this embodiment using the fourth condenser 84c described above, the holding process and alignment process described above are performed. The chuck stage 25 is rotated by the moving unit 30, the orientation of the pre-division line 14 of the wafer 10 is adjusted to be along the X-axis direction, and the processing start position of the pre-division line 14 of the wafer 10 is positioned directly below the fourth condenser 84c. When the pre-division line 14 is positioned directly below the fourth condenser 84c in the same manner as in the third embodiment described above, the height adjustment unit (not shown) is activated to adjust the height of the laser beam irradiation unit 8C to a predetermined height.

[0084] If the predetermined dividing line 14 of the wafer 10 is positioned directly below the fourth condenser 84c as described above, and the fourth condenser 84c is positioned at a predetermined height, the liquid supply unit 90 is activated, and liquid L is introduced from the liquid inlet 844c via the piping 92. The liquid L introduced from the liquid inlet 844c passes through the passage 89 within the wall portion 88 constituting the fourth condenser 84c, supplying liquid L to the lower end 86c side of the fourth condenser 84c. The liquid L supplied to the lower end 86c side of the fourth condenser 84c fills the space formed by the front surface 10a of the wafer 10 and the flat surface 85e of the hemisphere 85c, forming a liquid layer 851c. Thus, the hemisphere 85c is immersed in the liquid layer 851c.

[0085] If the fourth concentrator 84c, which includes the hemisphere 85c, is positioned at a predetermined height relative to the front surface 10a of the wafer 10 and a liquid layer 851c is formed, then while the wafer 10 is moved in the X-axis direction by the moving unit 30, the laser beam irradiation unit 8C is activated, and pulsed laser beam PL0 is irradiated under the same laser irradiation conditions as in the third embodiment described above. Figure 7 As shown in (b), the pulsed laser beam PL0 is guided to the focusing lens 841c of the fourth concentrator 84c for focusing, and then irradiates the spherical surface 85d of the hemisphere 85c. The hemisphere 85c, as described above, does not transmit the pulsed laser beam PL0 and is formed of a rigid component (metal, glass, etc.) that transmits vibrations. By irradiating the spherical surface 85d of the hemisphere 85c with the pulsed laser beam PL0, a shock wave PL3c is generated.

[0086] Shock wave PL3c generated by hemisphere 85c propagates within hemisphere 85c and reaches the flat surface 85d, generating shock wave PL3c in the liquid layer 851c. Furthermore, shock wave PL3c reaches the front surface 10a of wafer 10, further generating shock wave PL3c propagating within wafer 10. At this time, the shock wave PL3c propagating within wafer 10 converges at a predetermined depth Pz position P5 inside the pre-defined dividing line 14 of wafer 10 due to the action of the spherical surface 85d forming the upper surface of hemisphere 85c, forming a destructive layer S5. In this embodiment, when the pre-defined dividing line 14 of wafer 10 is positioned directly below the fourth concentrator 84c of the laser beam irradiation unit 8C as described above, the height of the laser beam irradiation unit 8C is adjusted to a predetermined height, which is the height at which the position P5 where the shock wave PL3c generated by hemisphere 85c converges inside wafer 10 to form the destructive layer S5 reaches the desired depth Pz. Furthermore, by operating the moving unit 30 in the aforementioned order, a breaking layer S5, serving as the starting point for dividing the wafer 10, can be formed inside all the predetermined dividing lines 14 of the wafer 10.

[0087] Based on the above Figure 7 The modified example of the third laser beam irradiation unit shown in (b) can also converge along the predetermined dividing line 14 of the wafer 10 at a position P5 set to a predetermined depth Pz to generate a destructive layer S5. It is not necessary to select a laser beam with absorbency or transmittance corresponding to the raw material of the wafer 10, and it is not necessary to prepare a laser processing device corresponding to the type of wafer or the type of processing.

[0088] Furthermore, in the above description, regarding the dome component 85b and hemisphere 85c, which function as shock wave generating units, for convenience, the shape of the portion irradiated by the pulsed laser light is referred to as a "sphere" or "sphere." However, in order to converge the shock wave generated by the pulsed laser light to the desired position, the curvature of the surface can be appropriately adjusted, and it is not limited to a perfectly spherical or spherical shape. Additionally, in the above embodiments, in any embodiment, the front surface 10a of the wafer 10 is used as the upper surface to irradiate the laser light or to propagate the shock wave generated by the laser light irradiation. However, the present invention is not limited to this; the back surface 10 of the wafer 10 can also be used as the upper surface and held in the chuck stage 25, and processing can be performed from the back surface 10b side of the wafer 10. Furthermore, in the second and third embodiments described above, the convergence point of the shock waves PL3a to PL3c can be located near the upper surface at the predetermined dividing line 14 of the wafer 10, and the upper surface of the wafer 10 can be processed like an ablation process.

Claims

1. A wafer processing method of dividing a wafer into individual chips, wherein the wafer processing method is configured to include the following steps: a holding step of holding the wafer in a holding unit; a damage layer forming step of positioning a convergence point of a shock wave at the wafer held in the holding unit to form a damage layer in a region to be divided; and a dividing step of dividing the wafer into individual chips using the damage layer as a starting point, in the damage layer forming step, a first laser light irradiation unit that irradiates pulsed laser light is used to form the laser light of each pulse into a ring shape having a time difference for each wavelength, the pulsed laser light formed into the ring shape is irradiated toward the wafer to generate a shock wave in the region to be divided to form the convergence point, the time difference is adjusted by the first laser light irradiation unit, and the position of the convergence point of the shock wave is set.

2. A wafer processing apparatus that divides a wafer into individual chips, wherein the wafer processing apparatus is configured to include: a holding unit that holds the wafer; and a damage layer forming unit that positions a convergence point of a shock wave at the wafer held in the holding unit to form a damage layer in a region to be divided, the damage layer forming unit is a first laser light irradiation unit that irradiates pulsed laser light, the first laser light irradiation unit is used to form the laser light of each pulse into a ring shape having a time difference for each wavelength, the pulsed laser light formed into the ring shape is irradiated toward the wafer to generate a shock wave in the region to be divided to form the convergence point, the time difference is adjusted by the first laser light irradiation unit, and the position of the convergence point of the shock wave is set. ​

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