Method for manufacturing a plurality of device chips

Abstract

The present invention provides a method of manufacturing a plurality of device chips, which prevents corner defects of the device chips in the case of thinning by grinding a workpiece and then dividing. The method has the following steps: a hole forming step of forming holes deeper than a finished thickness of each device chip in intersection portions where a plurality of division predetermined lines intersect, by irradiating a front surface side of the workpiece with a first laser beam having a wavelength absorbed by the workpiece; a front surface protection step of covering the front surface side of the workpiece with a protection member; an internal processing step of positioning a focal point of a second laser beam having a wavelength that transmits the workpiece inside the workpiece, and irradiating the second laser beam from a back surface side of the workpiece along each division predetermined line to form a region of relatively low intensity inside the workpiece; and a back surface side grinding step of grinding the back surface side of the workpiece until the finished thickness is reached to divide the workpiece into a plurality of device chips.

Description

TECHNICAL FIELD

[0001] The present application relates to a method of manufacturing a plurality of device chips by dividing a work along a plurality of division predetermined lines. BACKGROUND

[0002] In a process of manufacturing a device chip having a functional element such as an IC (Integrated Circuit) or an LSI (Large Scale Integration), a plurality of division predetermined lines are set in a lattice shape on a front surface side of a work having a substantially disc shape formed of a semiconductor such as silicon. After a functional element such as an IC or an LSI is formed in each region divided by the plurality of division predetermined lines, the work is divided along each division predetermined line.

[0003] In order to divide the work along each division predetermined line, a modification layer as a region in which mechanical strength is reduced is formed in the inside of the work in a manner along each division predetermined line, for example (see Patent Document 1). In order to form the modification layer, a laser processing apparatus is used.

[0004] The laser processing apparatus has a chuck table for holding the work. Above the chuck table, a laser beam irradiation unit capable of irradiating a pulsed laser beam having a wavelength that transmits through the work is provided.

[0005] In a state in which a focal point of the laser beam irradiated from the laser beam irradiation unit is positioned in the inside of the work, the chuck table is moved in a prescribed direction, thereby forming the modification layer in the inside of the work along the division predetermined line.

[0006] After the laser processing, the back surface side of the work is ground using a grinding apparatus. Thereby, the work is thinned, and is subjected to an external force to be divided along each division predetermined line with the modification layer as a fracture starting point. In this way, the work is divided into a plurality of device chips by the external force at the time of grinding.

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2006-12902

[0008] However, in the case where the back surface side of the work is ground using the grinding apparatus, in a cross portion where two division predetermined lines intersect, a defect is easily generated due to friction of the corner portions of the device chips with each other. In addition, in the case where the device chips are subjected to an external force, the defect generated in the corner portions can possibly develop to a region in which the functional element is formed. SUMMARY

[0009] The present application has been achieved in view of the problem, and has an object to provide a plurality of device chip manufacturing method which prevents a corner portion of a device chip from being damaged in a case where a workpiece is thinned by grinding and then divided.

[0010] According to one embodiment of the present application, there is provided a plurality of device chip manufacturing method of manufacturing a plurality of device chips from a workpiece in which devices are respectively formed in a plurality of regions divided by a plurality of division predetermined lines set in a lattice shape on a front surface side along each division predetermined line, wherein the plurality of device chip manufacturing method has: a hole forming step of forming a hole deeper than a finished thickness of each device chip in an intersection portion where the plurality of division predetermined lines intersect, by irradiating a first laser beam having a wavelength absorbed by the workpiece from an outside of the workpiece to the front surface side; a front surface protection step of covering the front surface side of the workpiece with a protection member; an internal processing step of forming a region having a lower intensity than a region where the second laser beam is not irradiated, in an inside of the workpiece, by positioning a focal point of a second laser beam having a wavelength that transmits through the workpiece at a position inside the workpiece on a back surface side deeper than the finished thickness, and irradiating the second laser beam from the back surface side along each division predetermined line; and a back surface side grinding step of grinding the back surface side of the workpiece until the workpiece becomes the finished thickness, and dividing the workpiece into a plurality of device chips.

[0011] Also, in the hole forming step, a non-through hole that does not pass through the back surface from the front surface can be formed as the hole.

[0012] Also, in the hole forming step, a non-through hole that does not pass through the back surface from the front surface can be formed as the hole.

[0013] In the plurality of device chip manufacturing method of one embodiment of the present application, the hole forming step forms a hole deeper than the finished thickness in the intersection portion, and thus it is possible to prevent the corners of the device chips from rubbing against each other in the back surface side grinding step. Thus, it is possible to prevent the generation of damage in the corners. In addition, it is possible to prevent the damage generated in the corners from developing to the region where the functional elements are formed. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is a perspective view of a wafer.

[0015] Figure 2 (A) of FIG. 1 is a view illustrating the hole forming step, Figure 2 (B) of FIG. 1 is an entire view of the front surface side of the wafer after the hole forming step, Figure 2 (C) of FIG. 1 is a partially enlarged view of the front surface side of the wafer after the hole forming step.

[0016] Figure 3 (A) is a diagram showing the internal processing steps. Figure 3 (B) is an overall view of the front side of the wafer after the internal processing steps. Figure 3 (C) is a magnified view of the front side of the wafer after the internal processing steps.

[0017] Figure 4 This is a partial cross-sectional side view of a wafer that illustrates the cleavage angles of the wafer.

[0018] Figure 5 (A) is a diagram showing the back-side grinding steps. Figure 5 (B) is an overall view of the front side of the wafer after the back-side grinding step. Figure 5 (C) is a partial magnified view of the front side of the wafer after the back-side grinding step.

[0019] Figure 6 It is a 3D diagram of the device chip.

[0020] Figure 7 It is a flowchart of the manufacturing process of multiple device chips.

[0021] Figure 8 This is a diagram illustrating the hole-forming steps of the second embodiment.

[0022] Figure 9 This is a flowchart of the manufacturing method according to the third embodiment.

[0023] Label Explanation

[0024] 11: Wafer; 11a: Front side; 11b: Back side; 13: Pre-defined dividing line; 15: Device; 17: Non-through hole; 19: Protective strip (protective component); 21, 21a: Modified layer; 21b: End; 23: Device chip; 25: Through hole; 27: Resin strip; 10: First laser beam irradiation unit; 12: Second laser beam irradiation unit; 14: Grinding unit; 16: Spindle; 18: Grinding wheel mounting base; 20: Grinding wheel; 22: Grinding wheel base; 24: Grinding tool; A: Depth; B: Depth; C: Diameter; D: Distance; L1: First laser beam; L2: Second laser beam. Detailed Implementation

[0025] Referring to the accompanying drawings, one embodiment of the present invention will be described. First, the wafer (workpiece) 11, which is the object of processing in the first embodiment, will be described. Figure 1 This is a 3D view of chip 11.

[0026] The wafer 11 is formed of a material such as silicon, for example, in a disc shape, and has a front surface 11a and a back surface 11b each of which is substantially circular. The front surface 11a side of the wafer 11 is divided into a plurality of regions by a plurality of division lines 13 which are set in a lattice shape in a manner of crossing each other.

[0027] A device 15 which is constituted of an IC (Integrated Circuit), an LSI (Large Scale Integration), or the like is formed on the front surface 11a side of each region divided by the plurality of division lines 13.

[0028] Further, the wafer 11 is not limited in material, shape, configuration, size, and the like. For example, the wafer 11 can be formed of a semiconductor other than silicon (GaAs, InP, GaN, SiC, or the like), sapphire, glass, or the like. Further, the device 15 is not limited in kind, number, shape, configuration, size, arrangement, and the like.

[0029] A circular resin tape (not shown) which is larger in diameter than the wafer 11 is attached to the back surface 11b side of the wafer 11. The resin tape has a laminated configuration of a base material layer and an adhesive layer (paste layer), for example, and the adhesive layer is attached to the back surface 11b side.

[0030] The base material layer is formed of polyolefin (PO), for example. The adhesive layer is formed on a part or the whole of one face of the base material layer. The adhesive layer is a resin of an ultraviolet hardening type, for example, and is formed of a resin of a rubber-based, an acrylic-based, a silicone-based, or the like.

[0031] However, the resin tape is not limited to the laminated configuration of the base material layer and the adhesive layer. For example, the resin tape can have only the base material layer. In this case, the resin tape is attached to the wafer 11 by thermocompression bonding the base material layer to the back surface 11b side of the wafer 11.

[0032] A metal annular frame which has an opening larger in diameter than the wafer 11 is attached to the outer peripheral portion of the resin tape. In this way, a wafer unit (not shown) in which the wafer 11 is supported by the resin tape to the annular frame is formed.

[0033] By forming the wafer unit, a conveyance pad (not shown) can convey the wafer 11 in a state of contacting the annular frame without contacting the wafer 11. However, in a case where the wafer 11 is conveyed using a Bernoulli-type conveyance pad (not shown) which can attract and hold the wafer 11 in a non-contact manner, the wafer unit can not be formed. That is, the resin tape can not be attached to the wafer 11.

[0034] Next, a manufacturing method of the plurality of device chips 23 of the first embodiment will be described. In the first embodiment, the wafer 11 is divided along the division- scheduled lines 13, thereby manufacturing a plurality of device chips 23 each having the device 15 (see FIG. 1). Note that Figure 6 ). In addition, Figure 7 is a flowchart of the manufacturing method of the plurality of device chips 23.

[0035] In the present embodiment, first, a non-through hole (hole forming step (S10)) which does not pass through the front surface 11a to the back surface 11b is formed at an intersection portion where a plurality of division-scheduled lines 13 intersect. Figure 2 of (A) is a view showing the hole forming step (S10).

[0036] In order to form the non-through hole 17, for example, a first laser processing device is used. The first laser processing device has a first chuck table (not shown) which attracts the back surface 11b side of the wafer 11 and holds it.

[0037] The first chuck table has, for example, a disc-shaped porous plate (not shown). The lower surface side of the porous plate is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed in the inside of the first chuck table. When the suction source is operated, a negative pressure is generated on the upper surface (holding surface) of the porous plate.

[0038] A horizontal movement mechanism (not shown) is provided below the first chuck table. The horizontal movement mechanism moves the first chuck table along a processing feed direction (X-axis direction) and an indexing feed direction (Y-axis direction).

[0039] A first laser beam irradiation unit 10 is provided above the first chuck table. The first laser beam irradiation unit 10 has a first laser oscillator (not shown) which generates a pulsed laser beam.

[0040] The first laser oscillator contains, for example, a laser medium such as Nd:YAG, Nd:YVO4, or the like which is suitable for laser oscillation. A first condenser (not shown) is connected to the first laser oscillator via a prescribed optical system.

[0041] The first condenser converges the laser beam emitted from the first laser oscillator to a prescribed position below the first condenser. The first laser beam L1 which is irradiated downward from the first condenser has a wavelength which is absorbed by the wafer 11 (for example, 355 nm, 532 nm, or 1064 nm).

[0042] In addition, the first laser beam L1 is adjusted, for example, in such a manner that the average output is 0.5 W or more and 50 W or less, the repetition frequency is 1 kHz or more and 200 kHz or less, and the spot diameter at the condensing point is 5 μm or more and 200 μm or less.

[0043] In addition, before the wafer 11 is processed using the first laser processing apparatus, a water-soluble resin coating cleaning apparatus (not shown) is used to coat the water-soluble resin on the front surface 11a side of the wafer 11. The water-soluble resin coating cleaning apparatus has a rotary stage (not shown) for attracting and holding the back surface 11b side of the wafer 11.

[0044] A rotary drive source such as a motor is provided below the rotary stage to rotate the rotary stage. In addition, a resin nozzle (not shown) for spraying the water-soluble resin is provided above the rotary stage. The water-soluble resin is, for example, PVA (polyvinyl alcohol), PEG (polyethylene glycol), PEO (polyethylene oxide), or the like.

[0045] In addition, a cleaning nozzle (not shown) for spraying a cleaning liquid such as pure water toward the front surface 11a side of the wafer 11 is provided in the vicinity of the resin nozzle. A drive source (not shown) is connected to the cleaning nozzle. The drive source reciprocally moves the cleaning nozzle in a circular arc shape on the front surface of the rotary stage.

[0046] In the hole forming step (S10), first, the rotary stage is rotated at, for example, 2000 rpm in a state where the back surface 11b side of the wafer 11 is attracted and held by the rotary stage of the water-soluble resin coating cleaning apparatus.

[0047] Further, when the water-soluble resin is sprayed from the resin nozzle after the resin nozzle is positioned on the front surface 11a side of the rotating wafer 11, the water-soluble resin spreads on the entire front surface 11a side by centrifugal force. In this way, the water-soluble resin is spin-coated on the entire front surface 11a side.

[0048] Then, the wafer unit is transported from the water-soluble resin coating cleaning apparatus to the first laser processing apparatus. In the present embodiment, the wafer 11 is transported in a state where the wafer 11 is not in contact with the wafer 11 but is in contact with the annular frame. In addition, in a case where the resin tape is not attached to the wafer 11, the wafer 11 is transported to the first laser processing apparatus using a Bernoulli-type transport pad after the water-soluble resin is dried.

[0049] Further, the back surface 11b side of the wafer 11 is attracted and held by the first chuck table. Next, the first laser beam irradiation unit 10 irradiates the first laser beam L1 from the outside of the wafer 11 toward the intersection portion on the front surface 11a side of the wafer 11.

[0050] The first laser beam L1 is condensed to the front surface 11a side, and thus the intersection portion on the front surface 11a side of the wafer 11 is ablation-processed. Thereby, a cylindrical non-through hole 17 having a depth B deeper than a depth A corresponding to a finished thickness of the device chip 23 is formed in the intersection portion.

[0051] When the non-through hole 17 is formed, the first chuck table is moved in a spiral shape at 1 mm / sec by the horizontal movement mechanism. For example, the focal point of the first laser beam LI is moved in a spiral shape from the outer periphery of the intersection to the center of the intersection.

[0052] After the non-through hole 17 is formed in all the intersections, the wafer unit is carried from the first laser processing device to the water-soluble resin coating cleaning device. In addition, in the case where the resin tape is not attached to the wafer 11, the wafer 11 is carried to the water-soluble resin coating cleaning device using a Bernoulli-type carrying pad. Also, in a state where the back surface lib side of the wafer 11 is held by being attracted by the rotary table, the rotary table is rotated at, for example, 2000 rpm.

[0053] Next, the cleaning nozzle is positioned on the front surface 11a side of the rotating wafer 11. The driving source is operated, whereby the cleaning nozzle is moved in a circular arc shape on the front surface 11a of the wafer 11 while the cleaning liquid is sprayed from the cleaning nozzle. Thus, the water-soluble resin is removed from the front surface 11a side together with the debris generated by the ablation.

[0054] Figure 2 (B) is an entire view of the front surface 11a side of the wafer 11 after the hole forming step (S10), Figure 2 (C) is a partial enlarged view of the front surface 11a side of the wafer 11 after the hole forming step (S10). In Figure 2 (B) and Figure 2 (C), the non-through hole 17 formed in the intersection of the division predetermined line 13 is shown by a black dot.

[0055] After the hole forming step (S10), in the case where the ultraviolet-hardening type adhesive layer is used in the resin tape attached to the back surface lib side, the back surface lib side is irradiated with ultraviolet rays to harden the adhesive layer. Thus, the adhesive force is reduced, so that the resin tape is easily peeled from the back surface lib side.

[0056] Next, a protective tape (protective member) 19 having a diameter larger than that of the wafer 11 and formed of resin is attached to the front surface 11a side of the wafer 11. The protective tape 19 has, for example, a stacked structure of a base material layer and an adhesive layer (paste layer), and the adhesive layer is attached to the front surface 11a side.

[0057] The base material layer is formed of, for example, polyolefin (PO). The adhesive layer is formed on a part or the entire one face of the base material layer. The adhesive layer is, for example, an ultraviolet-hardening type resin formed of a rubber-based, acrylic-based, silicone-based, or the like resin.

[0058] However, the protective tape 19 is not limited to the stacked structure of the base material layer and the adhesive layer. For example, the protective tape 19 can have only the base material layer. In this case, the base material layer is thermally pressure-bonded on the front surface 11a side of the wafer 11, and thereby the protective tape 19 is attached to the wafer 11.

[0059] After the protective tape 19 is attached to the front surface 11a side, the protective tape 19 is cut into a circular shape in such a manner that the protective tape 19 becomes substantially the same diameter as the wafer 11. Thereby, the front surface 11a side is covered with the protective tape 19 (front surface protection step (S20)). Then, the resin tape attached to the back surface 11b side is removed from the wafer 11.

[0060] After the front surface protection step (S20), a low-strength region (i.e., a modified layer) is formed inside the wafer 11 in such a manner that the modified layer is formed along the division predetermined line 13 (internal processing step (i.e., modified layer formation step) (S30)). Figure 3 FIG. 1 is a view showing the internal processing step (S30).

[0061] In order to form the modified layer 21 by the internal processing step (S30), for example, a second laser processing device is used. The second laser processing device has a second chuck table (not shown) that attracts and holds the back surface 11b side of the wafer 11.

[0062] The second chuck table has, for example, a porous plate (not shown) in a disc shape. The lower surface side of the porous plate is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed inside the second chuck table. When the suction source is activated, a negative pressure is generated on the upper surface (holding surface) of the porous plate.

[0063] A horizontal movement mechanism (not shown) is provided below the second chuck table. The horizontal movement mechanism moves the second chuck table in the processing feed direction (X-axis direction) and the indexing feed direction (Y-axis direction). In addition, a rotation drive source (not shown) for causing the second chuck table to rotate about a prescribed rotation axis is provided below the horizontal movement mechanism.

[0064] A second laser beam irradiation unit 12 is provided above the second chuck table. The second laser beam irradiation unit 12 has a second laser oscillator (not shown) that generates a pulsed laser beam.

[0065] The second laser oscillator contains, for example, a laser medium such as Nd:YVO4 that is suitable for laser oscillation. A second condenser (not shown) is connected to the second laser oscillator via a prescribed optical system.

[0066] The second condenser condenses the laser beam emitted from the second laser oscillator to a prescribed position. The second laser beam L2 irradiated from the second condenser has a wavelength (e.g., 1342 nm) that transmits through the wafer 11. The second laser beam L2 is adjusted, for example, in such a manner that the average output is 0.8 W or more and 3.2 W or less and the repetition frequency is 60 kHz or more and 140 kHz or less.

[0067] In the internal processing step (S30), first, the wafer 11 is held with the back surface 1 lb side exposed using the holding surface facing the front surface 11a side of the wafer 11. Next, the second laser beam L2 is irradiated to the wafer 11 from the back surface 1 lb side.

[0068] Also, in a state where the condensing point of the second laser beam L2 is positioned at one end of the separation intended line 13 and at a position inside the wafer 11 closer to the back surface 1 lb side than the depth B, the horizontal movement mechanism is operated to move the second chuck table in the X-axis direction.

[0069] The second chuck table is moved in the X-axis direction at a prescribed processing feed rate of, for example, 300 mm / sec or more and 1400 mm / sec or less, thereby moving the condensing point from one end to the other end of the separation intended line 13.

[0070] Multiphoton absorption occurs in the vicinity of the condensing point, forming a region (i.e., the modified layer 21) that is relatively low in strength (i.e., weak) than a region where the second laser beam L2 is not irradiated.

[0071] In the present embodiment, three modified layers 21 are formed along one separation intended line 13 by changing the depth position of the condensing point. However, the number of modified layers 21 formed along one separation intended line 13 is not limited to three, and can be two or four or more.

[0072] After three modified layers 21 are formed along one separation intended line 13, the second laser beam irradiation unit 12 is indexed in the Y-axis direction by a prescribed length, and the irradiation position of the second laser beam L2 is positioned at another separation intended line 13.

[0073] Next, the condensing point of the second laser beam L2 is moved along the other separation intended line 13 to form three modified layers 21 inside the wafer 11 that differ in depth position as with one separation intended line 13. After three modified layers 21 are formed inside the wafer 11 along all of the separation intended lines 13 that are substantially parallel to the X-axis direction, the second chuck table is rotated by 90°.

[0074] Also, similarly to the case of the first laser beam Ll, the focal point of the second laser beam L2 is moved along the X-axis direction in a manner along each of the division intended lines 13, and three modification layers 21 are formed inside the wafer 11 in a manner along each of the division intended lines 13. In this way, the modification layers 21 are formed inside the wafer 11 in a manner along all of the division intended lines 13.

[0075] Figure 3 (B) is an entire view of the front surface 11a side of the wafer 11 after the internal processing step (S30), Figure 3 (C) is an enlarged view of a part of the front surface 11a side of the wafer 11 after the internal processing step (S30). In Figure 3 (B) and Figure 3 (C), the modification layers 21 are indicated by broken lines.

[0076] In addition, in the case where a silicon wafer of a single crystal is used as the wafer 11, the wafer 11 has cleavage properties, and cleavage is performed at a specific angle. Figure 4 is a partial cross-sectional side view of the wafer 11 that illustrates the cleavage angle of the wafer 11.

[0077] Generally, the (100) plane of a silicon wafer is used as the front surface 11a of the wafer 11. Therefore, in the case where the bottom of the non-through hole 17 is parallel to the front surface 11a, the plane that constitutes the bottom of the non-through hole 17 is also the (100) plane. In contrast, the cleavage plane of a silicon wafer is, for example, the (111) plane.

[0078] In the example shown in Figure 4 , the bottom surface of the non-through hole 17 is a circle with a diameter C, and the plurality of modification layers 21 are formed in a manner that passes directly below the center of the bottom surface of the non-through hole 17. The angle θ that the (111) plane and the (100) plane make at the end portion 21b on the front surface 11a side of the modification layer 21a, which is located at the position closest to the front surface 11a among the plurality of modification layers 21, is represented by arccos((3) -1 / 2 ) and is approximately 54.7 degrees.

[0079] The distance D from the end portion 21b to the bottom surface of the non-through hole 17 is represented by D = (C / 2) • tan θ, and therefore, for example, in the case where the diameter C is 30 μm, the distance D is approximately 21 μm. Cleavage in the (111) plane direction occurs from the end portion 21b as a starting point, and therefore, by forming the plurality of modification layers 21 in a manner that the end portion 21b is located at a position closer to the front surface 11a than a depth of approximately 21 μm from the bottom surface of the non-through hole 17, it is possible to prevent a crack that develops from the end portion 21b from reaching the front surface 11a.

[0080] After the internal processing step (S30), the back surface 11b side of the wafer 11 is ground (back surface side grinding step (S40)). Figure 5FIG. 4 is a view showing the back surface side grinding step (S40). In order to grind the back surface 1 lb side, a grinding device is used.

[0081] The grinding device has a 3rd chuck table (not shown) for attracting and holding the wafer 11. The 3rd chuck table has, for example, a porous plate (not shown) in a disc shape.

[0082] The lower surface side of the porous plate is connected to a suction source (not shown) such as an ejector via a flow path (not shown) formed in the inside of the 3rd chuck table. When the suction source is activated, a negative pressure is generated on the upper surface (holding surface) of the porous plate.

[0083] A rotary drive source (not shown) such as a motor is linked to the lower portion of the 3rd chuck table. In addition, a grinding unit 14 is provided above the 3rd chuck table. The grinding unit 14 has a spindle housing (not shown) to which a lifting mechanism (not shown) for lifting the grinding unit 14 in the Z-axis direction is linked.

[0084] A portion of a spindle 16 is rotatably housed in the spindle housing. A motor for driving the spindle 16 is linked to one end of the spindle 16. The other end of the spindle 16 protrudes from the spindle housing, and a disc-shaped grinding wheel mounting seat 18 is fixed to the other end.

[0085] A grinding wheel 20 having substantially the same diameter as the grinding wheel mounting seat 18 is mounted on the lower surface of the grinding wheel mounting seat 18. The grinding wheel 20 has a ring-shaped grinding wheel base 22 formed of a metal material such as aluminum or stainless steel.

[0086] The upper surface side of the grinding wheel base 22 is fixed to the grinding wheel mounting seat 18, so that the grinding wheel base 22 is mounted to the spindle 16. A plurality of grinding tools 24 is provided on the lower surface side of the grinding wheel base 22. The plurality of grinding tools 24 is arranged in a ring shape on the periphery of the lower surface of the grinding wheel base 22 in such a manner that gaps are provided between adjacent grinding tools 24.

[0087] Each grinding tool 24 is formed by mixing abrasive grains such as diamond, cBN (cubic boron nitride), or the like in a bonding material such as metal, ceramic, resin, or the like. However, the bonding material or the abrasive grains are not limited, and can be appropriately selected in accordance with the specifications of the grinding tool 24.

[0088] A plurality of openings (not shown) for supplying grinding water such as pure water to the grinding tools 24 is formed on the lower surface side of the grinding wheel base 22 at a position inward of the plurality of grinding tools 24. In addition, instead of providing the openings for supplying the grinding water on the lower surface side of the grinding wheel base 22, a grinding water supply nozzle (not shown) can be provided above the 3rd chuck table.

[0089] In the back surface side grinding step (S40), first, the front surface 11a side of the wafer 11 is suction-held by the holding surface of the 3rd chuck table with the protective tape 19 interposed. And, while the 3rd chuck table is rotated at, for example, 10 rpm and the grinding wheel 20 is rotated at 3000 rpm in a prescribed direction respectively, the grinding wheel 20 is processed fed downward at a prescribed speed (for example, 0.6 μm / s) by the lifting mechanism.

[0090] Thus, the grinding tool 24 is pressed to the back surface 11b side of the wafer 11 to grind the back surface 11b side until the back surface 11b side of the wafer 11 becomes a prescribed finished thickness. In addition, during grinding, grinding water is supplied to the grinding tool 24 at a prescribed flow rate of, for example, 3.0 L / min or more and 7.0 L / min or less.

[0091] When stress is imparted to the wafer 11 during grinding, a crack (not shown) develops toward the front surface 11a and the back surface 11b with the modification layer 21 as a dividing starting point. The crack reaches the front surface 11a and the back surface 11b of the wafer 11, thereby dividing the wafer 11 into a plurality of device chips 23 (refer to FIG. 8). Figure 6 ).

[0092] Figure 5 (B) of FIG. 8 is an entire view of the front surface 11a side of the wafer 11 after the back surface side grinding step (S40), Figure 5 (C) of FIG. 8 is a partially enlarged view of the front surface 11a side of the wafer 11 after the back surface side grinding step (S40). Figure 6 is a perspective view of the device chip 23. The device chip 23 is formed with a recess at each of the four corners thereof corresponding to a portion of the side wall of the non-through hole 17.

[0093] In the 1st embodiment, the non-through hole 17 having a depth B deeper than a depth A corresponding to the finished thickness is formed at the intersection portion by the hole forming step (S10), so it is possible to prevent the corner portions of the device chips 23 from rubbing against each other during the back surface side grinding step (S40).

[0094] Thus, it is possible to prevent the generation of defects at the corner portions of the device chips 23. In addition, it is possible to prevent the defects generated at the corner portions of the device chips 23 from developing to the region where the device 15 (functional element) is formed. Thus, for example, compared to the case where the non-through hole 17 is not formed on the wafer 11, it is possible to improve the bending strength of the device chip 23.

[0095] As described above, in the hole forming step (S10) of the present embodiment, the non-through hole 17 is formed by laser ablation using the first laser beam irradiation unit 10. In contrast, in the etching process using an expensive photomask or the like, the photomask needs to be set depending on the kind of the pattern formed on the wafer 11. Therefore, in the present embodiment, there is an advantage that the design of the position, shape, and the like of the non-through hole 17 can be flexibly changed compared to the etching process.

[0096] In addition, in the present embodiment, the non-through hole 17 is formed, and therefore, for example, there is an advantage that the time required for the hole forming step (S10) can be shortened compared to the case where a through hole is formed. Next, the second embodiment in which a through hole is formed will be described.

[0097] In the hole forming step (S10) of the second embodiment, a through hole that penetrates from the front surface 11a to the back surface 11b of the wafer 11 is formed instead of the non-through hole 17. This aspect is different from the first embodiment. The other aspects are the same as those of the first embodiment.

[0098] Figure 8 is a view that shows the hole forming step (S10) of the second embodiment. In addition, in Figure 8 , the resin tape 27 that constitutes the wafer unit is shown as being attached to the front surface 11a side.

[0099] In the hole forming step (S10) of the second embodiment, the water-soluble resin is first spin-coated on the entire front surface 11a side. Next, the first laser beam L1 is irradiated to the intersection portion on the front surface 11a side using the first laser beam irradiation unit 10, and the through hole 25 is formed in the intersection portion.

[0100] In the case where the through hole 25 is formed, the first chuck table is moved in a spiral shape by the horizontal movement mechanism. At this time, for example, if the first chuck table is moved at a machining feed speed slower than that of the first embodiment, the through hole 25 can be formed in the wafer 11. In addition, it is also possible to make the average output of the first laser beam L1 higher than that of the first embodiment after the machining feed speed is made the same as that of the first embodiment.

[0101] After the through hole 25 is formed in all the intersection portions, the wafer unit is transported to the water-soluble resin coating and cleaning device, and the wafer 11 is cleaned. In this way, the wafer 11 in which the through hole 25 is formed in each intersection portion can be formed.

[0102] Next, the third embodiment will be described. Figure 9 is a flowchart of the manufacturing method of the third embodiment. In the third embodiment, after the front surface protecting step (S20) and the internal processing step (S30), the hole forming step (S35) is performed.

[0103] More specifically, after the internal processing step (S30), a circular resin tape (not shown) larger than the diameter of the wafer 11 is attached on the back surface 1 lb side, and a ring-shaped frame is attached to the outer peripheral portion of the resin tape. Then, the protective tape 19 attached to the front surface 11a side in the front surface protection step (S20) is peeled off (back surface protection step (S33)).

[0104] After the back surface protection step (S33), the hole forming step (S35) is performed similarly to the hole forming step (S10) of the first embodiment. Thus, the non-through hole 17 is formed at each of the intersecting portions of the division intended line 13.

[0105] Also, after the hole forming step (S35), the front surface 11a side is again covered with the protective tape 19, and the resin tape attached to the back surface 1 lb side is peeled off (additional front surface protection step (S37)).

[0106] After the additional front surface protection step (S37), the back surface side grinding step (S40) is performed similarly to the first embodiment, and the wafer 11 is ground to the finished thickness. In the third embodiment as well, the corner portions of the device chips 23 can be prevented from rubbing against each other in the back surface side grinding step (S40), and thus the generation of defects at the corner portions of the device chips 23 can be prevented.

[0107] Next, the fourth embodiment will be described. In the fourth embodiment, a through hole 25 is formed instead of the non-through hole 17 in the hole forming step (S35) of the third embodiment, similarly to the second embodiment. This aspect is different from the third embodiment. The other aspects are the same as the third embodiment.

[0108] In the fourth embodiment as well, the corner portions of the device chips 23 can be prevented from rubbing against each other in the back surface side grinding step (S40), and thus the generation of defects at the corner portions of the device chips 23 can be prevented. Other than this, the configurations, methods, and the like of the above-described embodiments can be appropriately changed and implemented within a range not deviating from the object of the present application.

Claims

1. A method for manufacturing multiple device chips, wherein a workpiece on its front side, in which devices are respectively formed in multiple regions divided by multiple predetermined dividing lines arranged in a grid pattern, is divided into individual device chips along each predetermined dividing line, thereby manufacturing multiple device chips from the workpiece, characterized in that, The manufacturing method of these multiple device chips includes the following steps: In the hole forming step, a first laser beam having a wavelength absorbed by the workpiece is irradiated from the outside of the workpiece toward the front side, forming a hole at the intersection of multiple predetermined dividing lines with a depth greater than the finished thickness of each device chip. The front protection step involves covering the front side of the workpiece with a protective component. In the internal processing step, with the focus point of a second laser beam having a wavelength that transmits through the workpiece positioned inside the workpiece at a position closer to the back side of the workpiece than the depth equivalent to the finished thickness, the second laser beam is irradiated from the back side along each predetermined dividing line. This forms a modified layer region inside the workpiece with a lower intensity than the region not irradiated by the second laser beam. The distance of the entire modified layer from the front side of the workpiece is greater than the depth of the hole formed in the hole forming step, and the depth of the hole is greater than the depth equivalent to the finished thickness of each device chip. as well as The back-side grinding step involves grinding the back side of the workpiece until it reaches the finished thickness, and then dividing the workpiece into multiple device chips.

2. The method for manufacturing multiple device chips according to claim 1, characterized in that, In the hole forming step, a non-through hole that does not extend from the front side to the back side is formed as the hole.

3. The method for manufacturing multiple device chips according to claim 1, characterized in that, In the hole forming step, a through hole is formed from the front side to the back side as the hole.

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