JP7845962B2 - Device chip manufacturing method - Google Patents

Description

This invention relates to a method for manufacturing a device chip.

In recent years, to improve the processing power of semiconductor chips such as ICs (Integrated Circuits) and LSIs (Large Scale Integrations), semiconductor wafers have been put into practical use in which semiconductor chips are formed by laminating a low-dielectric constant insulating film (Low-k film) and a functional layer on the surface of a semiconductor substrate such as silicon. Furthermore, semiconductor wafers have also been put into practical use in which a metal pattern, consisting of a metal film called a TEG (Test Element Group), is partially arranged on the semiconductor wafer's network, allowing for testing of the circuit's functionality through the metal pattern before the semiconductor wafer is divided.

To divide such wafers into chips, a method has been proposed (Patent Document 1) in which a laser beam with a wavelength that absorbs the laminate is irradiated from the surface side of the wafer to form processing grooves, and a laser beam with a wavelength that transmits to the substrate is irradiated from the back side of the wafer to form a modified layer inside the substrate, and then the wafer is divided by applying an external force to this wafer. When processing a wafer with multiple intersecting streets formed on its surface side using the above method, conventionally, a first processing groove is first formed along a first direction, then a second processing groove is formed along a second direction, then a first modified layer is formed along the first direction, and then a second modified layer is formed along the second direction.

Japanese Patent Publication No. 2007-173475

When a laser beam is used to form a processing groove on the wafer surface, debris generated adheres to the vicinity of both sides of the formed groove. Therefore, when forming a second processing groove, the processing occurs over the debris adhering to the vicinity of the first processing groove at the intersection of the streets. This results in a shallower groove depth near the intersection of the second processing groove, and the laminate may remain without being removed. In such cases, when forming the second modification layer, the laser beam is reflected or scattered along the second direction by the already formed first modification layer at the intersection of the streets. This increases the amount of light leaking onto the wafer surface in the streets formed along the second direction. It is known that this can cause the laminate remaining from the processing groove formation to be irradiated with the leaked light generated during the formation of the modification layer near the intersection of the streets, potentially causing the laminate to delaminate.

This invention has been made in view of the above problems, and its objective is to provide a method for manufacturing a device chip that can suppress delamination of the laminate due to light leakage when processing a wafer in which multiple intersecting streets have been formed.

To solve the above-mentioned problems and achieve the objective, the present invention provides a method for manufacturing a device chip, comprising: dividing a wafer on which a functional layer is laminated on the surface of a substrate to form a plurality of devices along a plurality of first division lines that demarcate the plurality of devices and a plurality of second division lines that intersect the first division lines to form a device chip, the method comprising: a first processing groove formation step of irradiating a laser beam of a wavelength absorbent to the functional layer from the surface side of the wafer along the first division lines to form a first processing groove; and after performing the first processing groove formation step, irradiating a laser beam of a wavelength absorbent to the functional layer from the surface side of the wafer along the second division lines to form a second The method is characterized by comprising: a second groove formation step of forming a processing groove; a first modified layer formation step of irradiating the back side of the wafer with a laser beam of a wavelength that is transparent to the substrate along the second planned division line after performing the second groove formation step to form a first modified layer inside the substrate; a second modified layer formation step of irradiating the back side of the wafer with a laser beam of a wavelength that is transparent to the substrate along the first planned division line after performing the first modified layer formation step to form a second modified layer inside the substrate; and a division step of applying an external force to the wafer to divide it along the first planned division line and the second planned division line after performing the second modified layer formation step.

This invention can suppress delamination of the laminate due to light leakage when processing a wafer in which multiple intersecting streets have been formed.

Figure 1 is a perspective view showing an example of a wafer to be processed by the device chip manufacturing method according to the embodiment. Figure 2 is a cross-sectional view of the wafer shown in Figure 1. Figure 3 is a flowchart showing the flow of the manufacturing method for a device chip according to the embodiment. Figure 4 is a perspective view showing one state of the first groove formation step shown in Figure 3. Figure 5 is a plan view showing the wafer after the first groove formation step shown in Figure 3. Figure 6 is a plan view showing an enlarged portion of the wafer shown in Figure 5. Figure 7 is a cross-sectional view taken along the line A-A' in Figure 6. Figure 8 is a cross-sectional view taken along the line B-B' in Figure 6. Figure 9 is a plan view showing the wafer after the second groove formation step shown in Figure 3. Figure 10 is a plan view showing an enlarged portion of the wafer shown in Figure 9. Figure 11 is a cross-sectional view taken along the line B-B' in Figure 10. Figure 12 is a perspective view showing one state of the first modified layer formation step shown in Figure 3. Figure 13 is a plan view showing the wafer after the first modified layer formation step shown in Figure 3. Figure 14 is a cross-sectional view along the first modified layer in the wafer shown in Figure 13. Figure 15 is a plan view showing the wafer after the second modified layer formation step shown in Figure 3. Figure 16 is a cross-sectional view of the wafer shown in Figure 15, along the second modified layer. Figure 17 is a side view showing a partial cross-section of one state of the division step shown in Figure 3. Figure 18 is a side view showing a partial cross-section of one state of the division step after Figure 17. Figure 19 is a perspective view showing another example of the division steps shown in Figure 3.

The embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments described below. Furthermore, the components described below include those that are easily conceivable to those skilled in the art, and those that are substantially the same. Moreover, the components described below can be combined as appropriate. In addition, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the present invention.

[Embodiment]
A method for manufacturing a device chip 18 according to an embodiment of the present invention will be described with reference to the drawings. Figure 1 is a perspective view showing an example of a wafer 10 to be processed in the manufacturing method of the device chip 18 according to the embodiment. Figure 2 is a cross-sectional view of the wafer 10 shown in Figure 1. The wafer 10 shown in Figures 1 and 2 is a disc-shaped semiconductor device wafer, optical device wafer, _etc. , with a substrate 11 made of silicon (Si), sapphire ( _Al₂O₃ ), gallium arsenide (GaAs), silicon carbide (SiC), or lithium tantalate ( _LiTaO₃ ), etc.

The wafer 10 has a first division line 13 and a second division line 14 set on its surface 12. The first division line 13 extends in a first direction 21 and is set in multiple locations along a second direction 22 perpendicular to the first direction 21. The second division line 14 extends in a second direction 22 and is set in multiple locations along the first direction 21.

The wafer 10 has a device 15 formed in a region demarcated by a first division line 13 and a second division line 14, which are set in a grid pattern. The device 15 is, for example, an integrated circuit such as an IC or LSI, or an image sensor such as a CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor).

Furthermore, the wafer 10 has a functional layer 16 laminated on the surface 12 of the substrate 11. The functional layer 16 is composed of a Low-k film, which is made up of an inorganic film such as SiOF or BSG (SiOB), or an organic film such as a polymer film such as polyimide or parylene, and a conductive film made of a conductive metal. The Low-k film is laminated with the conductive film to form the device 15. The conductive film constitutes the circuit of the device 15. Therefore, the device 15 is composed of Low-k films laminated together and conductive films laminated between the Low-k films.

The wafer 10 is transported and processed while supported, for example, by an annular frame 30 and tape 31. The frame 30 is an annular plate member made of metal or resin, with an opening larger than the outer diameter of the wafer 10. The tape 31 is expandable and in sheet form, with an outer diameter larger than the opening of the frame 30. The tape 31 is attached to the back side of the frame 30 so as to cover the opening of the frame 30. The wafer 10 is fixed to the frame 30 and tape 31 by positioning it at a predetermined location within the opening of the frame 30 and attaching its back side 17 to the tape 31.

Furthermore, the tape 31 may be composed of, for example, a base layer made of an expandable synthetic resin and an adhesive layer laminated on the base layer and made of an expandable and adhesive synthetic resin, or it may be composed of a thermoplastic resin without an adhesive layer.

The wafer 10 is divided into individual devices 15 along a plurality of first division lines 13 and a plurality of second division lines 14 to be manufactured into device chips 18. In this embodiment, the device chip 18 is square in shape, but it may also be rectangular. Furthermore, in this embodiment, the wafer 10 is disc-shaped, but in this invention, it does not have to be disc-shaped.

Figure 3 is a flowchart showing the flow of a manufacturing method for a device chip 18 according to an embodiment. The manufacturing method for the device chip 18 is a method for manufacturing multiple device chips 18 from a wafer 10 to be processed. As shown in Figure 3, the manufacturing method for the device chip 18 includes a first processing groove formation step 1, a second processing groove formation step 2, a first modified layer formation step 3, a second modified layer formation step 4, and a splitting step 5.

(First machining groove formation step 1)
Figure 4 is a perspective view showing one state of the first machining groove formation step 1 shown in Figure 3. Figure 5 is a plan view showing the wafer 10 after the first machining groove formation step 1 shown in Figure 3. Figure 6 is a plan view showing an enlarged portion of the wafer 10 in Figure 5. Figure 7 is a cross-sectional view taken along line A-A' in Figure 6. Figure 8 is a cross-sectional view taken along line B-B' in Figure 6.

The cross-sectional view along line A-A' is a cross-sectional view perpendicular to the first planned division line 13 and passing through the device 15; that is, it is a cross-sectional view parallel to the second planned division line 14 and not on the second planned division line 14. The cross-sectional view along line B-B' is a cross-sectional view that does not pass through the device 15 but follows the second planned division line 14. Therefore, in the cross-sectional view along line B-B', the side of the device 15 is visible towards the back in the depth direction of the paper. The first processing groove formation step 1 is a step in which a laser beam 40 is irradiated from the surface 12 side of the wafer 10 along the first planned division line 13 to form the first processing groove 23.

As shown in Figure 4, in the first groove formation step 1 of the embodiment, a first groove 23 along the first planned division line 13 is formed on the surface 12 side of the wafer 10 by ablation processing using a laser processing apparatus 45. The laser beam 40 irradiated toward the wafer 10 in the first groove formation step 1 is a laser beam with a wavelength that is absorbed by the functional layer 16.

The laser processing apparatus 45 comprises a chuck table 46, a laser beam irradiation unit 47, an imaging unit 48, and a moving unit (not shown) that moves the chuck table 46 and the laser beam irradiation unit 47 relative to each other. In this embodiment, the processing feed direction of the laser processing apparatus 45 is the X-axis direction, which represents one direction in the horizontal plane. The indexing feed direction of the laser processing apparatus 45 is the Y-axis direction, which represents a direction perpendicular to the X-axis direction in the horizontal plane.

In the first groove formation step 1, the back surface 17 of the wafer 10 is first held on the holding surface (upper surface) of the chuck table 46 via the tape 31. The holding surface of the chuck table 46 is, for example, a disc-shaped surface formed from porous ceramic or the like, and is a plane parallel to the horizontal direction. The holding surface is connected to a vacuum suction source via a vacuum suction path. The chuck table 46 holds the wafer 10 placed on the holding surface by suction. The laser processing apparatus 45 may include, for example, a plurality of clamping members arranged around the chuck table 46, and the frame 30 supporting the wafer 10 may be clamped by the clamping members.

In the first machining groove formation step 1, the chuck table 46 is then moved to the machining position by a moving unit. Next, the first planned division line 13 is detected by imaging the wafer 10 with the imaging unit 48. Once the first planned division line 13 is detected, the chuck table 46 is rotated around the vertical axis to align the first direction 21 along which the first planned division line 13 of the wafer 10 follows with the machining feed direction (X-axis direction) of the laser machining apparatus 45. Simultaneously, an alignment is performed using a moving unit (not shown) to align the first planned division line 13 with the irradiation section of the laser beam irradiation unit 47.

In the first processing groove formation step 1, the focal point 41 of the laser beam 40 is positioned near the functional layer 16 on the surface 12 of the wafer 10. While irradiating the wafer 10 from the surface 12 side with the laser beam 40, the focal point 41 is moved relative to the first planned division line 13 in the processing feed direction. This forms the first processing groove 23 along the first planned division line 13, and as shown in Figures 7 and 8, the functional layer 16 is removed along the first planned division line 13, exposing the substrate 11.

During this process, debris 19 generated by the ablation process adheres to the vicinity of both sides of the first planned division line 13 in the width direction. More specifically, as shown in Figures 6 and 7, the debris 19 adheres to the first planned division line 13, generally between the first processing groove 23 and the device 15. Furthermore, as shown in Figures 6 and 8, the debris 19 also adheres to both sides of the first planned division line 13 at the intersection perpendicular to the second planned division line 14, at a position extending along the longitudinal direction of the first planned division line 13. That is, in the longitudinal direction of the second planned division line 14, at both ends of the portion where it intersects with the first planned division line 13, the debris 19 adheres so as to traverse the second planned division line 14.

After forming the first machining groove 23 on one of the first division lines 13, the focusing point 41 is moved relative to the indexing feed direction (Y-axis direction), i.e., the second direction 22, and the first machining groove 23 is similarly formed on the adjacent first division lines 13. As shown in Figure 5, once the first machining groove 23 has been formed on all of the first division lines 13, the first machining groove formation step 1 is completed, and the process moves to the second machining groove formation step 2.

(Second machining groove formation step 2)
Figure 9 is a plan view showing the wafer 10 after the second processing groove formation step 2 shown in Figure 3. Figure 10 is a plan view showing an enlarged portion of the wafer 10 in Figure 9. Figure 11 is a cross-sectional view taken along line B-B' in Figure 10. Figure 11 shows the same cross-section as Figure 8, that is, a cross-section that does not pass through the device 15 but passes over the second planned division line 14. The second processing groove formation step 2 is performed after the first processing groove formation step 1 is performed. The second processing groove formation step 2 is a step in which a laser beam 40 is irradiated from the surface 12 side of the wafer 10 along the second planned division line 14 to form a second processing groove 24.

In the second groove formation step 2 of the embodiment, a second groove 24 is formed on the surface 12 side of the wafer 10 along the second planned division line 14 by ablation processing using the laser processing apparatus 45 shown in Figure 4. The laser beam 40 irradiated toward the wafer 10 in the second groove formation step 2 is a laser beam with a wavelength that is absorbed by the functional layer 16.

In the second machining groove formation step 2, the chuck table 46 is first rotated around its vertical axis to align the second direction 22 along which the second planned division line 14 of the wafer 10 follows with the machining feed direction (X-axis direction) of the laser processing device 45. Simultaneously, an alignment is performed using a moving unit (not shown) to align the second planned division line 14 with the irradiation section of the laser beam irradiation unit 47.

In the second machining groove formation step 2, the focal point 41 of the laser beam 40 is positioned near the functional layer 16 on the surface 12 of the wafer 10. While irradiating the wafer 10 from the surface 12 side with the laser beam 40, the focal point 41 is moved relative to the second planned division line 14 in the machining feed direction. This forms a second machining groove 24 along the second planned division line 14, and as shown in Figure 11, the functional layer 16 is removed along the second planned division line 14, exposing the substrate 11.

At this point, the laser beam 40 is also irradiated onto the debris 19 generated in the first processing groove formation step 1 at the point where the second planned division line 14 intersects with the first planned division line 13. That is, the laser is then used to further cut across the two rows of debris 19 adhering longitudinally along the second planned division line 14, as shown in Figures 6 and 8, to form the second processing groove 24, as shown in Figure 10. As a result, as shown in Figure 11, in the areas where debris 19 is adhering to the second planned division line 14—that is, just before and after the intersection with the first processing groove 23 (to the left and right of the first processing groove 23 shown in Figure 11)—the groove depth of the second processing groove 24 becomes shallower than in other areas, and the functional layer 16 remains (hereinafter, the remaining functional layer 16 will be referred to as the functional layer 161).

After forming a second machining groove 24 on one of the second division lines 14, the focusing point 41 is moved relative to the indexing feed direction (Y-axis direction), i.e., the first direction 21, and a second machining groove 24 is similarly formed on the adjacent second division lines 14. As shown in Figure 9, once the second machining grooves 24 have been formed on all the second division lines 14, the second machining groove formation step 2 is completed, and the process moves to the first modified layer formation step 3.

(First modified layer formation step 3)
Figure 12 is a perspective view showing one state of the first modified layer formation step 3 shown in Figure 3. Figure 13 is a plan view showing the wafer 10 after the first modified layer formation step 3 shown in Figure 3. Figure 14 is a cross-sectional view of the wafer 10 in Figure 13 along the first modified layer 25. Note that Figure 14 shows the same cross-section as the cross-sectional view along line B-B' shown in Figures 8 and 11, that is, a cross-sectional view that does not pass through the device 15 but along the second planned division line 14 (second processing groove 24). The first modified layer formation step 3 is performed after the second processing groove formation step 2 is performed. The first modified layer formation step 3 is a step in which a laser beam 40 is irradiated from the back surface 17 side of the wafer 10 along the second planned division line 14 to form the first modified layer 25 inside the substrate 11.

A modified layer refers to a region whose density, refractive index, mechanical strength, or other physical properties differ from those of the surrounding area. Examples of modified layers include melted regions, cracked regions, dielectric breakdown regions, refractive index change regions, and regions where these regions are mixed. The modified layer has lower mechanical strength, etc., than other parts of the wafer 10.

As shown in Figure 12, in the first modified layer formation step 3 of the embodiment, a first modified layer 25 is formed inside the substrate 11 of the wafer 10 along the second planned division line 14 by stealth dicing using a laser processing apparatus 45. The laser beam 40 irradiated toward the wafer 10 in the first modified layer formation step 3 is a laser beam with a wavelength that is transparent to the substrate 11.

In the first modified layer formation step 3, the tape 31 that was attached to the wafer 10 in the first processing groove formation step 1 and the second processing groove formation step 2 is first peeled off from the back surface 17 of the wafer 10, and a new tape 31 is attached to the front surface 12 of the wafer 10. Next, the front surface 12 of the wafer 10 is held in place by suction to the holding surface (upper surface) of the chuck table 46 via the tape 31.

In the first modified layer formation step 3, the chuck table 46 is then moved to the processing position by a moving unit. Next, the wafer 10 is imaged by the imaging unit 48 to detect the second planned division line 14. Once the second planned division line 14 is detected, the chuck table 46 is rotated around its vertical axis to align the second direction 22 along which the second planned division line 14 of the wafer 10 follows with the processing feed direction (X-axis direction) of the laser processing apparatus 45. Simultaneously, an alignment is performed using a moving unit (not shown) to align the second planned division line 14 with the irradiation section of the laser beam irradiation unit 47.

In the first modified layer formation step 3, with the focal point 41 of the laser beam 40 positioned inside the substrate 11 of the wafer 10, the laser beam 40 is irradiated from the back surface 17 side of the wafer 10, while the focal point 41 is moved relative to the second planned division line 14 in the processing feed direction. As a result, the first modified layer 25 is formed along the second processing groove 24, as shown in Figures 13 and 14.

The first modified layer 25 is formed before the second modified layer 26 (see Figures 15 and 16), which will be described later. Therefore, in the first modified layer formation step 3, scattering of the laser beam 40 due to irradiation of another modified layer does not occur. Consequently, the stray light from this scattered laser beam 40 does not irradiate the remaining functional layer 161 shown in Figure 14.

After forming the first modified layer 25 on one of the second planned division lines 14, the focusing point 41 is moved relative to the indexing and feeding direction (Y-axis direction), i.e., the first direction 21, and the first modified layer 25 is similarly formed on the adjacent second planned division lines 14. As shown in Figure 13, once the first modified layer 25 has been formed on all of the second planned division lines 14, the first modified layer formation step 3 is completed, and the process moves on to the second modified layer formation step 4.

(Second modified layer formation step 4)
Figure 15 is a plan view showing the wafer 10 after the second modification layer formation step 4 shown in Figure 3. Figure 16 is a cross-sectional view of the wafer 10 in Figure 15 along the second modification layer 26. Note that Figure 16 is a cross-sectional view perpendicular to the cross-section of the B-B' line shown in Figures 8, 11, and 14, and does not pass through the device 15, but along the first planned division line 13 (first processing groove 23). The second modification layer formation step 4 is performed after the first modification layer formation step 3 is performed. The second modification layer formation step 4 is a step in which a laser beam 40 is irradiated from the back surface 17 side of the wafer 10 along the first planned division line 13 to form a second modification layer 26 inside the substrate 11.

In the second modified layer formation step 4 of the embodiment, a second modified layer 26 is formed inside the substrate 11 of the wafer 10 along the first planned division line 13 by stealth dicing using the laser processing apparatus 45 shown in Figure 12. The laser beam 40 irradiated toward the wafer 10 in the second modified layer formation step 4 is a laser beam with a wavelength that is transparent to the substrate 11.

In the second modified layer formation step 4, the chuck table 46 is first rotated around its vertical axis to align the first direction 21 along which the first planned division line 13 of the wafer 10 follows with the processing feed direction (X-axis direction) of the laser processing device 45. Simultaneously, an alignment is performed using a moving unit (not shown) to align the first planned division line 13 with the irradiation section of the laser beam irradiation unit 47.

In the second modified layer formation step 4, with the focal point 41 of the laser beam 40 positioned inside the substrate 11 of the wafer 10, the laser beam 40 is irradiated from the back surface 17 side of the wafer 10, while the focal point 41 is moved relative to the first planned division line 13 in the processing feed direction. As a result, a second modified layer 26 is formed along the first processing groove 23, as shown in Figures 15 and 16.

In this process, as shown in Figure 16, the first modified layer 25 is already formed on the first planned division line 13 where the second planned division line 14 intersects with the first planned division line 13, which will form the second modified layer 26. Therefore, at the point where the first planned division line 13 intersects with the second planned division line 14, the laser beam 40 is irradiated onto the first modified layer 25 formed in the first modified layer formation step 3. As a result, a portion of the laser beam 40 is reflected in the first modified layer 25 in a direction along the first planned division line 13, increasing the amount of stray light along the first planned division line 13.

Here, the first machining groove 23 formed on the first planned division line 13 is formed before the second machining groove 24; that is, the laser beam 40 is not irradiated onto the debris 19 during the first machining groove formation step 1. Therefore, in the second machining groove 24, as shown in Figure 14, the functional layer 161 remains, whereas in the first machining groove 23 formed on the first planned division line 13, as shown in Figure 16, the functional layer 161 is completely removed. This prevents stray light from the laser beam 40 along the first planned division line 13 from irradiating the remaining functional layer 161.

After forming the second modified layer 26 on one of the first planned division lines 13, the focusing point 41 is moved relative to the indexing and feeding direction (Y-axis direction), i.e., the second direction 22, and the second modified layer 26 is similarly formed on the adjacent first planned division lines 13. As shown in Figure 15, once the second modified layer 26 has been formed on all of the first planned division lines 13, the second modified layer formation step 4 is completed, and the process moves on to the division step 5.

(Division Step 5)
Figure 17 is a side view showing a partial cross-section of one state of the splitting step 5 shown in Figure 3. Figure 18 is a side view showing a partial cross-section of one state of the splitting step 5 after Figure 17. Splitting step 5 is performed after the second modified layer formation step 4 is carried out. Splitting step 5 is a step in which an external force is applied to the wafer 10 to split it along the first planned splitting line 13 and the second planned splitting line 14.

As shown in Figures 17 and 18, in the splitting step 5 of the embodiment, the wafer 10 is split by the expansion device 50 applying an external force radially to the tape 31. The expansion device 50 comprises a chuck table 51, a clamp member 52, a lifting unit 53, a push-up member 54, and a roller member 55. The push-up member 54 is cylindrical in shape and is provided coaxially with and on the outer circumference of the chuck table 51. The roller member 55 is rotatably provided on the same plane as or slightly above the holding surface of the chuck table 51 and at the upper end of the push-up member 54.

As shown in Figure 17, in the splitting step 5, first, the surface 12 side of the wafer 10 is placed on the holding surface (upper surface) of the chuck table 51 via the tape 31, and the outer circumference of the frame 30 is fixed with the clamp member 52. At this time, the roller member 55 abuts against the tape 31 between the inner edge of the frame 30 and the outer edge of the wafer 10.

As shown in Figure 18, in the splitting step 5, the lifting unit 53 then raises the chuck table 51 and the push-up member 54 together. At this time, since the outer circumference of the tape 31 is fixed by the clamp member 52 via the frame 30, the portion between the inner edge of the frame 30 and the outer edge of the wafer 10 expands in the planar direction. Furthermore, the roller member 55 provided at the upper end of the push-up member 54 reduces friction with the tape 31.

In splitting step 5, as a result of the expansion of the tape 31, radial tensile forces act on the tape 31. When radial tensile forces act on the tape 31, as shown in Figure 18, the wafer 10 to which the tape 31 is attached is split using the second modified layer 26 along the first planned splitting line 13 and the first modified layer 25 along the second planned splitting line 14 as fracture points, and is fragmented into device chips 18. After the wafer 10 has been split into device chips 18, for example, in a pickup process, the device chips 18 are picked up from the tape 31 using a well-known picker.

(Variation of step 5 of division)
Figure 19 is a perspective view showing another example of the splitting step 5 shown in Figure 3. As shown in Figure 19, in the modified splitting step 5, the wafer 10 is split by applying an external force that presses the wafer 10 by grinding the back surface 17 side of the wafer 10 with the grinding device 60. The grinding device 60 includes a chuck table 61, a spindle 62, a grinding wheel 63, a grinding wheel 64, and a grinding water supply nozzle (not shown). The grinding wheel 63 is attached to the lower end of the spindle 62, which is a rotating shaft member. The grinding wheel 64 is mounted on the lower surface of the grinding wheel 63.

In the splitting step 5 shown in Figure 19, first, the surface 12 side of the wafer 10 is held by suction against the holding surface (upper surface) of the chuck table 61. Next, with the chuck table 61 rotating around its axis, the grinding wheel 63 is rotated around its axis. The grinding wheel 63 rotates on an axis parallel to the axis of the chuck table 61.

Next, grinding water is supplied from a grinding water supply nozzle (not shown), and the grinding wheel 64 mounted on the underside of the grinding wheel 63 is brought closer to the chuck table 61 at a predetermined feed rate. This grinds the wafer 10 from the back surface 17 side with the grinding wheel 64, thinning the wafer 10 to a predetermined finish thickness.

At this point, the wafer 10 is pressed by the grinding wheel 63's grinding wheel 64, causing cracks to extend from the second modified layer 26 and the first modified layer 25 to the bottom of the first and second processing grooves 23 and 24. This separates the substrate 11 and the functional layer 16 along the first and second planned division lines 13 and 14, resulting in individual device chips 18. Subsequently, similar to the division step 5 shown in Figures 17 and 18, the device chips 18 are picked up from the tape 31 using a well-known picker, for example, in a pickup process.

As explained above, near the intersection of the first planned division line 13 and the second planned division line 14, it is known that in the second machining groove formation step 2, machining is performed on the debris 19 generated in the first machining groove formation step 1. This can cause the laser beam 40 to be blocked by the debris 19, resulting in the functional layer 16 located directly beneath the debris 19 remaining on the second planned division line 14 (see functional layer 161 in Figure 11, etc.). Furthermore, in the second modified layer formation step 4, it is known that the laser beam 40, reflected or scattered by the first modified layer 25 formed in the first modified layer formation step 3, is irradiated in the machining feed direction.

In the manufacturing method of the device chip 18 according to this embodiment, the processing order for the first planned division line 13 and the second planned division line 14 is reversed compared to the processing order for the modified layer formation. That is, in the second modified layer formation step 4, the laser beam 40 reflected or scattered by the first modified layer 25 formed in the first modified layer formation step 3 is irradiated onto the first planned division line 13 along the first processing groove 23, and irradiation of the functional layer 161 remaining on the second planned division line 14 can be suppressed. In this way, it is possible to avoid the overlap between the remaining area of the functional layer 161 and the area where stray light occurs, thus contributing to a reduction in peeling of the functional layer 16 and improving processing quality.

Furthermore, when performing ablation on the second planned division line 14, if the laser beam 40 output is increased or the processing speed is reduced to prevent the functional layer 16 from remaining, the damage to the wafer 10 may increase, potentially leading to a decrease in flexural strength. In this invention, even if the functional layer 161 remains on the second planned division line 14, the leakage light from the laser beam 40 can be suppressed from irradiating the remaining functional layer 161, eliminating the need to change the laser processing intensity.

The present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the invention. For example, in the first modified layer formation step 3 and the second modified layer formation step 4, the laser beam 40 may be irradiated through the sheet 31 attached to the back surface 17 side of the wafer 10. That is, after the second processing groove formation step 2, the wafer 10 may be held in place by suction on the chuck table 46 without removing the tape 31 from the back surface 17 side of the wafer 10. In this case, it is preferable to attach a sheet-like holding member to the front surface 12 side of the wafer 10 to protect the device 15.

10 Wafer 11 Substrate 12 Front surface 13 First planned division line 14 Second planned division line 15 Device 16, 161 Functional layer 17 Back surface 18 Device chip 19 Debris 21 First direction 22 Second direction 23 First processing groove 24 Second processing groove 25 First modified layer 26 Second modified layer 40 Laser beam

Claims (1)

A method for manufacturing a device chip, comprising dividing a wafer on which a functional layer is laminated on the surface of a substrate to form a plurality of devices along a plurality of first division lines that demarcate the plurality of devices and a plurality of second division lines that intersect the first division lines,
A first processing groove forming step involves irradiating the wafer surface with a laser beam of a wavelength that is absorbable to the functional layer along the first planned division line to form a first processing groove,
After performing the first groove formation step, a second groove formation step is performed, in which a laser beam with a wavelength that is absorbed by the functional layer is irradiated from the surface side of the wafer along the second planned division line to form a second groove.
After performing the second processing groove formation step, a first modification layer formation step is performed, in which a laser beam with a wavelength that is transparent to the substrate is irradiated from the back side of the wafer along the second planned division line to form a first modification layer inside the substrate.
After performing the first modified layer formation step, a second modified layer formation step is performed, in which a laser beam of a wavelength that is transparent to the substrate is irradiated from the back side of the wafer along the first planned division line to form a second modified layer inside the substrate.
After performing the second modified layer formation step, a splitting step is performed in which an external force is applied to the wafer to split it along the first planned splitting line and the second planned splitting line,
A method for manufacturing a device chip, characterized by comprising the following features.