CN112420608A - Method for manufacturing multiple device chips - Google Patents

Method for manufacturing multiple device chips Download PDF

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Publication number
CN112420608A
CN112420608A CN202010825811.0A CN202010825811A CN112420608A CN 112420608 A CN112420608 A CN 112420608A CN 202010825811 A CN202010825811 A CN 202010825811A CN 112420608 A CN112420608 A CN 112420608A
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China
Prior art keywords
wafer
front surface
workpiece
laser beam
device chips
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CN202010825811.0A
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Chinese (zh)
Inventor
松冈祐哉
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Disco Corp
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Disco Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/77—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate
    • H01L21/78—Manufacture or treatment of devices consisting of a plurality of solid state components or integrated circuits formed in, or on, a common substrate with subsequent division of the substrate into plural individual devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/36—Removing material
    • B23K26/38—Removing material by boring or cutting
    • B23K26/382—Removing material by boring or cutting by boring
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
    • H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
    • H01L21/304—Mechanical treatment, e.g. grinding, polishing, cutting
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/67—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere
    • H01L21/683—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping
    • H01L21/6835—Apparatus specially adapted for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus specially adapted for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components ; Apparatus not specifically provided for elsewhere for supporting or gripping using temporarily an auxiliary support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2221/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof covered by H01L21/00
    • H01L2221/67—Apparatus for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components; Apparatus not specifically provided for elsewhere
    • H01L2221/683—Apparatus for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components; Apparatus not specifically provided for elsewhere for supporting or gripping
    • H01L2221/68304—Apparatus for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components; Apparatus not specifically provided for elsewhere for supporting or gripping using temporarily an auxiliary support
    • H01L2221/68327—Apparatus for handling semiconductor or electric solid state devices during manufacture or treatment thereof; Apparatus for handling wafers during manufacture or treatment of semiconductor or electric solid state devices or components; Apparatus not specifically provided for elsewhere for supporting or gripping using temporarily an auxiliary support used during dicing or grinding

Abstract

The invention provides a method for manufacturing a plurality of device chips, which prevents corner parts of the device chips from being damaged when a processed object is ground, thinned and divided. The method comprises the following steps: a hole forming step of irradiating the front side of the object with a 1 st laser beam having a wavelength absorbed by the object to form a hole deeper than a depth corresponding to a finished thickness of each device chip at an intersection where the plurality of planned dividing lines intersect; 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 condensing point of a 2 nd laser beam having a wavelength transmitting through the object to be processed inside the object to be processed, and irradiating the 2 nd laser beam from the back side of the object to be processed along each line to form a region having a relatively low intensity inside the object to be processed; and a back side grinding step of grinding the back side of the workpiece until the back side reaches a finish thickness, and dividing the workpiece into a plurality of device chips.

Description

Method for manufacturing multiple device chips
Technical Field
The present invention relates to a method for manufacturing a plurality of device chips by dividing a workpiece along a plurality of lines to be divided.
Background
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 lines to be divided are first set in a lattice shape on the front side of a substantially disk-shaped object to be processed made of a semiconductor such as silicon. Next, after functional devices such as ICs and LSIs are formed in the respective regions defined by the plurality of lines to divide the workpiece along the lines to divide the workpiece.
In order to divide the workpiece along each line to be divided, for example, a modified layer which is a region having reduced mechanical strength is first formed inside the workpiece so as to extend along each line to be divided (see, for example, patent document 1). To form the modified layer, a laser processing apparatus is used.
The laser processing apparatus includes a chuck table for holding a workpiece. A laser beam irradiation unit capable of irradiating a pulse-shaped laser beam having a wavelength transmitting through the workpiece is provided above the chuck table.
The chuck table is moved in a predetermined direction while positioning a converging point of the laser beam irradiated from the laser beam irradiation unit inside the workpiece, thereby forming a modified layer inside the workpiece along the line to be divided.
After the laser processing, the rear surface side of the workpiece is ground using a grinding apparatus. Thus, the workpiece is thinned and divided along the lines to be divided by the modified layer serving as a fracture start point under external force. In this way, the workpiece is divided into a plurality of device chips by the external force at the time of grinding.
Patent document 1: japanese patent laid-open publication No. 2006-12902
However, when the back surface side of the workpiece is ground using the grinding apparatus, the corners of the device chip are likely to be chipped due to friction between the corners at the intersection where the two planned dividing lines intersect. When the device chip receives an external force, the defect generated in the corner may progress to the region where the functional element is formed.
Disclosure of Invention
The present invention has been made in view of the above problems, and an object thereof is to provide a method for manufacturing a plurality of device chips, which prevents the corner portions of the device chips from being chipped when the workpiece is cut by grinding and thinning the workpiece.
According to one aspect of the present invention, there is provided a method of manufacturing a plurality of device chips by dividing a workpiece, in which devices are formed on a front surface side in a plurality of regions defined by a plurality of planned dividing lines set in a lattice shape, into device chips along planned dividing lines, and manufacturing the plurality of device chips from the workpiece, the method including: a hole forming step of irradiating the 1 st laser beam having a wavelength absorbed by the workpiece from the outside of the workpiece to the front surface side to form a hole deeper than a depth corresponding to a finished thickness of each device chip at an intersection where the plurality of planned dividing lines intersect; a front surface protecting step of covering the front surface side of the workpiece with a protective member; an internal processing step of irradiating the 2 nd laser beam from the back side along each line to form a region having a lower intensity than a region not irradiated with the 2 nd laser beam in the inside of the object, while positioning a converging point of the 2 nd laser beam having a wavelength transmitted through the object at a position inside the object, the position being located on the back side of the object with respect to a depth corresponding to the finish thickness; and a back side grinding step of grinding the back side of the workpiece until the workpiece reaches the finish thickness, and dividing the workpiece into a plurality of device chips.
In the hole forming step, a non-through hole that does not penetrate from the front surface to the back surface may be formed as the hole.
In the hole forming step, a through hole penetrating from the front surface to the rear surface may be formed as the hole.
In the method for manufacturing a plurality of device chips according to one aspect of the present invention, since the hole having a depth deeper than the finish thickness is formed at the intersection in the hole forming step, the corners of the device chips can be prevented from rubbing against each other in the back-side grinding step. Therefore, the corner portion can be prevented from being chipped. Further, defects generated in the corner portions can be prevented from progressing to the regions where the functional elements are formed.
Drawings
Fig. 1 is a perspective view of a wafer.
Fig. 2 (a) is a view showing a hole forming step, fig. 2 (B) is an overall view of the front side of the wafer after the hole forming step, and fig. 2 (C) is a partial enlarged view of the front side of the wafer after the hole forming step.
Fig. 3 (a) is a view showing an internal processing step, fig. 3 (B) is a whole view of the front surface side of the wafer after the internal processing step, and fig. 3 (C) is a partial enlarged view of the front surface side of the wafer after the internal processing step.
Fig. 4 is a partial cross-sectional side view of a wafer illustrating the angle of cleaving of the wafer.
Fig. 5 (a) is a view showing a back-side grinding step, fig. 5 (B) is a whole view of the front side of the wafer after the back-side grinding step, and fig. 5 (C) is a partial enlarged view of the front side of the wafer after the back-side grinding step.
Fig. 6 is a perspective view of the device chip.
Fig. 7 is a flow chart of a method of manufacturing a plurality of device chips.
Fig. 8 is a diagram showing a hole forming step of embodiment 2.
Fig. 9 is a flowchart of the manufacturing method of embodiment 3.
Description of the reference symbols
11: a wafer; 11 a: a front side; 11 b: a back side; 13: dividing the predetermined line; 15: a device; 17: a non-through hole; 19: a protective tape (protective member); 21. 21 a: a modified layer; 21 b: an end portion; 23: a device chip; 25: a through hole; 27: a resin tape; 10: 1 st laser beam irradiation unit; 12: a 2 nd laser beam irradiation unit; 14: a grinding unit; 16: a main shaft; 18: a grinding wheel mounting seat; 20: grinding the grinding wheel; 22: a grinding wheel base station; 24: grinding the grinding tool; a: depth; b: depth; c: a diameter; d: a distance; l is1: 1 st laser beam; l is2: the 2 nd laser beam.
Detailed Description
An embodiment of one embodiment of the present invention will be described with reference to the drawings. First, a wafer (workpiece) 11 to be processed in embodiment 1 will be described. Fig. 1 is a perspective view of a wafer 11.
The wafer 11 is formed into a disk shape using a material such as silicon, and has a front surface 11a and a back surface 11b each having a substantially circular shape. The front surface 11a of the wafer 11 is divided into a plurality of regions by a plurality of lines to divide (streets) 13 set in a grid shape so as to intersect each other.
On the front surface 11a side of each region divided by the plurality of planned dividing lines 13, a device 15 including an IC (Integrated Circuit), an LSI (Large Scale Integration), or the like is formed.
The material, shape, structure, size, and the like of the wafer 11 are not limited. For example, the wafer 11 may be formed of a material such as a semiconductor other than silicon (GaAs, InP, GaN, SiC, or the like), sapphire, or glass. In addition, the kind, number, shape, structure, size, arrangement, and the like of the devices 15 are not limited.
A circular resin tape (not shown) having a diameter larger than that of the wafer 11 is attached to the back surface 11b side of the wafer 11. The resin tape has, for example, a laminated structure of a base material layer and an adhesive layer (paste layer) attached to the back surface 11b side.
The base material layer is formed of, for example, Polyolefin (PO). The adhesive layer is formed on a part of one surface of the base material layer or integrally therewith. The adhesive layer is, for example, an ultraviolet-curable resin, and is formed of a resin such as a rubber-based, acrylic-based, or silicone-based resin.
However, the resin tape is not limited to the laminated structure of the base material layer and the adhesive layer. For example, the resin tape may have only a base material layer. In this case, the base material layer is thermocompression bonded to the back surface 11b side of the wafer 11, whereby the resin tape is bonded to the wafer 11.
A metal ring frame having an opening larger than the diameter of the wafer 11 is attached to the outer periphery of the resin tape. In this way, a wafer unit (not shown) in which the wafer 11 is supported by the ring frame via the resin tape is formed.
By forming the wafer unit, the transfer pad (not shown) can transfer the wafer 11 in a state of not contacting the wafer 11 but contacting the ring frame. However, when the wafer 11 is transported using a bernoulli type transport pad (not shown) capable of sucking and holding the wafer 11 in a non-contact manner, a wafer unit may not be formed. That is, the resin tape may not be attached to the wafer 11.
Next, a method for manufacturing the plurality of device chips 23 according to embodiment 1 will be described. In embodiment 1, the wafer 11 is divided along the lines to divide 13, thereby manufacturing a plurality of device chips 23 each having a device 15 (see fig. 6). Fig. 7 is a flowchart of a method for manufacturing the plurality of device chips 23.
In the present embodiment, first, a non-through hole that does not penetrate from the front surface 11a to the rear surface 11b is formed at an intersection where the plurality of lines to divide 13 intersect (hole forming step (S10)). Fig. 2 (a) is a diagram showing the hole forming step (S10).
For example, the 1 st laser processing apparatus is used to form the non-through hole 17. The 1 st laser processing apparatus includes a 1 st chuck table (not shown) for sucking and holding the back surface 11b side of the wafer 11.
The 1 st chuck table has, for example, a disk-shaped porous plate (not shown). The lower surface side of the porous plate is connected to a suction source (not shown) such as an injector via a flow path (not shown) formed inside the 1 st chuck table. When the suction source is operated, a negative pressure is generated on the upper surface (holding surface) of the porous plate.
A horizontal movement mechanism (not shown) is provided below the 1 st chuck table. The horizontal movement mechanism moves the 1 st chuck table in a machining feed direction (X-axis direction) and an indexing feed direction (Y-axis direction).
A 1 st laser beam irradiation unit 10 is disposed above the 1 st chuck table. The 1 st laser beam irradiation unit 10 includes a 1 st laser oscillator (not shown) that generates a pulsed laser beam.
The 1 st laser oscillator includes, for example, Nd: YAG, Nd: YVO4Etc. laser media. The 1 st laser oscillator is connected to a 1 st condenser (not shown) via a predetermined optical system.
The 1 st condenser condenses the laser beam emitted from the 1 st laser oscillatorThe beam is converged to a predetermined position below the 1 st condenser. 1 st laser beam L irradiated downward from 1 st condenser1Having a wavelength that is absorbed by the wafer 11 (e.g., at 355nm, 532nm, or 1064 nm).
In addition, the 1 st laser beam L1For example, the average output is 0.5W to 50W, the repetition frequency is 1kHz to 200kHz, and the spot diameter at the condensing point is 5 μm to 200 μm.
Before the wafer 11 is processed by the 1 st laser processing apparatus, a water-soluble resin is applied to the front surface 11a of the wafer 11 by a water-soluble resin application and cleaning apparatus (not shown). The water-soluble resin coating and cleaning apparatus has a rotary table (not shown) for sucking and holding the back surface 11b side of the wafer 11.
A rotary drive source such as a motor for rotating the rotary table is provided below the rotary table. A resin nozzle (not shown) for spraying a water-soluble resin is provided above the rotary table. Examples of the water-soluble resin include PVA (polyvinyl alcohol), PEG (polyethylene glycol), PEO (polyethylene oxide), and the like.
Further, a cleaning nozzle (not shown) for jetting a cleaning liquid such as pure water toward the front surface 11a 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 reciprocates the cleaning nozzle in an arc shape on the front surface of the rotary table.
In the hole forming step (S10), first, the rotary table of the water-soluble resin coating and cleaning apparatus is rotated at 2000rpm, for example, while the wafer 11 is held by suction on the back surface 11b side.
Further, when the water-soluble resin is ejected 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 over the entire front surface 11a side by the centrifugal force. Thus, the water-soluble resin is spin-coated on the entire front surface 11a side.
Then, the wafer unit is transported from the water-soluble resin coating and cleaning apparatus to the 1 st laser processing apparatus. In the present embodiment, the wafer 11 is transported in a state of being not in contact with the wafer 11 but in contact with the ring frame. In the case where no resin tape is attached to the wafer 11, the wafer 11 is conveyed to the 1 st laser processing apparatus using a bernoulli type conveying pad after the water-soluble resin is dried.
Then, the wafer 11 is held by suction on the back surface 11b side by the 1 st chuck table. Then, the 1 st laser beam L is irradiated from the outside of the wafer 11 to the intersection on the front surface 11a side of the wafer 11 by the 1 st laser beam irradiation unit 101。
Making the 1 st laser beam L1Converging to the front surface 11a side, thereby performing ablation processing on the intersection portion of the front surface 11a side of the wafer 11. Thereby, a columnar non-through hole 17 is formed at the intersection, and the non-through hole 17 has a depth B deeper than a depth a corresponding to the finish thickness of the device chip 23.
When the non-through hole 17 is formed, the 1 st chuck table is moved in a vortex shape by a horizontal movement mechanism at 1 mm/sec. For example, by using the 1 st laser beam L1The converging point of (2) moves from the outer periphery of the intersection to the center of the intersection in a spiral shape.
After the non-through holes 17 are formed at all the intersections, the wafer unit is transported from the 1 st laser processing apparatus to the water-soluble resin application and cleaning apparatus. When no resin tape is attached to the wafer 11, the wafer 11 is transported to the water-soluble resin application and cleaning apparatus using a bernoulli type transport pad. Then, the rotary table is rotated at, for example, 2000rpm in a state where the back surface 11b side of the wafer 11 is sucked and held by the rotary table.
Next, the cleaning nozzle is positioned on the front surface 11a side of the rotating wafer 11. The cleaning nozzle is operated to eject the cleaning liquid from the cleaning nozzle while reciprocating the cleaning nozzle in an arc shape on the front surface 11a of the wafer 11. Thereby, the water-soluble resin is removed from the front surface 11a side together with the debris generated by ablation.
Fig. 2 (B) is an overall view of the front surface 11a side of the wafer 11 after the hole forming step (S10), and fig. 2 (C) is a partially enlarged view of the front surface 11a side of the wafer 11 after the hole forming step (S10). In fig. 2 (B) and 2 (C), the non-through holes 17 formed at the intersections of the lines to divide 13 are illustrated by black dots.
When an ultraviolet-curing adhesive layer is used for the resin tape attached to the back surface 11b side after the hole forming step (S10), the back surface 11b side is irradiated with ultraviolet rays to cure the adhesive layer. This reduces the adhesive strength, and therefore the resin tape is easily peeled from the rear surface 11b side.
Next, a protective tape (protective member) 19 having a diameter larger than the diameter of the wafer 11 and made of resin is joined to the front surface 11a side of the wafer 11. The protective tape 19 has, for example, a laminated structure of a base material layer and an adhesive layer (paste layer) bonded to the front surface 11a side.
The base material layer is formed of, for example, Polyolefin (PO). An adhesive layer is formed on a part or the whole of one surface of the base material layer. The adhesive layer is, for example, an ultraviolet-curable resin, and is formed of a resin such as a rubber-based, acrylic-based, or silicone-based resin.
However, the protective tape 19 is not limited to the laminated structure of the base material layer and the adhesive layer. For example, the protective tape 19 may have only a base material layer. In this case, the substrate layer is thermocompression bonded to the front surface 11a side of the wafer 11, and the protective tape 19 is bonded to the wafer 11.
After the protective tape 19 is pasted to the front surface 11a side, the protective tape 19 is cut into a circular shape so that the diameter of the protective tape 19 becomes substantially the same as that of the wafer 11. Thereby, the front surface 11a side is covered with the protective tape 19 (front surface protecting step (S20)). Then, the resin tape attached to the back surface 11b side is removed from the wafer 11.
After the front surface protecting step (S20), a region having a low strength (i.e., a modified layer) is formed inside the wafer 11 so as to extend along the planned dividing line 13 (an internal processing step (i.e., a modified layer forming step) (S30)). Fig. 3 (a) is a diagram showing the internal processing step (S30).
In order to form the modified layer 21 by the internal processing step (S30), for example, a 2 nd laser processing apparatus is used. The 2 nd laser processing apparatus includes a 2 nd chuck table (not shown) for sucking and holding the back surface 11b side of the wafer 11.
The 2 nd chuck table has, for example, a disk-shaped porous plate (not shown). The lower surface side of the porous plate is connected to a suction source (not shown) such as an injector via a flow path (not shown) formed inside the 2 nd chuck table. When the suction source is operated, a negative pressure is generated on the upper surface (holding surface) of the porous plate.
A horizontal movement mechanism (not shown) is provided below the 2 nd chuck table. The horizontal movement mechanism moves the 2 nd chuck table in a machining feed direction (X-axis direction) and an indexing feed direction (Y-axis direction). A rotation drive source (not shown) for rotating the 2 nd chuck table about a predetermined rotation axis is provided below the horizontal movement mechanism.
A 2 nd laser beam irradiation unit 12 is disposed above the 2 nd chuck table. The 2 nd laser beam irradiation unit 12 includes a 2 nd laser oscillator (not shown) that generates a pulsed laser beam.
The 2 Nd laser oscillator includes, for example, Nd: YVO4Etc. laser media. A 2 nd condenser (not shown) is connected to the 2 nd laser oscillator via a predetermined optical system.
The 2 nd condenser condenses the laser beam emitted from the 2 nd laser oscillator to a predetermined position. 2 nd laser beam L irradiated from 2 nd condenser2Having a wavelength (e.g., 1342nm) that is transmitted through wafer 11. 2 nd laser beam L2For example, the average output is adjusted to 0.8W to 3.2W, and the repetition frequency is adjusted to 60kHz to 140 kHz.
In the inner processing step (S30), the front surface 11a side of the wafer 11 is held by the holding surface so that the rear surface 11b side is exposed. Next, the 2 nd laser beam L is irradiated to the wafer 11 from the back surface 11b side2。
Then, the 2 nd laser beam L is applied2The second chuck table is moved in the X-axis direction by operating the horizontal moving mechanism in a state where the light converging point of (2) is positioned at one end of the line to divide (13) and inside the wafer (11) on the back surface (11B) side of the depth (B).
For example, the 2 nd chuck table is moved in the X-axis direction at a predetermined processing feed speed of 300 mm/sec or more and 1400 mm/sec or less, and the converging point is moved from one end to the other end of the line to divide 13.
Generating multiphoton absorption near the light-converging point to form a 2 nd laser beam L2The region of (a) is low in strength (i.e., brittle), and therefore a region of relatively low strength (i.e., the modified layer 21) is formed so as to follow the path of movement of the converging point.
In the present embodiment, three modified layers 21 are formed along one line to divide 13 by changing the depth position of the condensed point. However, the number of the modified layers 21 formed along one line to divide 13 is not limited to three, and may be two, or four or more.
After three modified layers 21 are formed along one line 13, the 2 nd laser beam irradiation unit 12 is indexed by a predetermined length in the Y axis direction, and the 2 nd laser beam L is fed2Is positioned on the other planned dividing lines 13.
Next, the 2 nd laser beam L is caused to follow the other planned dividing lines 132The converging point of (2) is moved to form three modified layers 21 having different depth positions in the wafer 11, similarly to the one line to divide 13. After three modified layers 21 are formed inside the wafer 11 along all the planned dividing lines 13 substantially parallel to the X-axis direction, the 2 nd chuck table is rotated by 90 °.
Similarly, the 2 nd laser beam L is caused to follow the planned dividing lines 132The converging point of (2) is moved in the X-axis direction, and three modified layers 21 are formed inside the wafer 11 so as to be along the planned dividing lines 13. In this way, the modified layer 21 is formed inside the wafer 11 so as to extend along all the lines to divide 13.
Fig. 3 (B) is an overall view of the front surface 11a side of the wafer 11 after the internal processing step (S30), and fig. 3 (C) is a partially enlarged view of the front surface 11a side of the wafer 11 after the internal processing step (S30). In fig. 3 (B) and 3 (C), the modified layer 21 is indicated by a broken line.
When a single-crystal silicon wafer is used as the wafer 11, the wafer 11 has cleavage properties and is cleaved at a specific angle. Fig. 4 is a partial cross-sectional side view of wafer 11 illustrating the angle of cleaving of wafer 11.
The (100) face of the silicon wafer is generally used as the front face 11a of the wafer 11. Therefore, when the bottom of the non-through hole 17 is parallel to the front surface 11a, the surface constituting the bottom of the non-through hole 17 is also a (100) surface. On the other hand, the cleavage plane of the silicon wafer is, for example, a (111) plane.
In the example shown in fig. 4, the bottom surface of the non-through hole 17 is a circle having a diameter C, and the plurality of modified layers 21 are formed so as to pass directly below the center of the bottom surface of the non-through hole 17. An angle θ formed by a (111) plane and a (100) plane, through which an end 21b of the modified layer 21a on the front surface 11a side, located closest to the front surface 11a side among the plurality of modified layers 21, passes, is arccos ((3)-1/2) Representing approximately 54.7 degrees.
Since 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, for example, when the diameter C is 30 μm, the distance D is about 21 μm. (111) Since the cleavage in the plane direction occurs with the end portion 21b as a starting point, the plurality of modified layers 21 are formed so that the end portion 21b is located on the front surface 11a side of the depth of about 21 μm from the bottom surface of the non-through hole 17, and thus, a crack that has progressed from the end portion 21b can be prevented from reaching the front surface 11 a.
After the internal processing step (S30), the back surface 11b side of the wafer 11 is ground (back surface side grinding step (S40)). Fig. 5 (a) is a view showing the back side grinding step (S40). In order to grind the back surface 11b side, a grinding apparatus is used.
The grinding apparatus includes a 3 rd chuck table (not shown) for holding the wafer 11 by suction. The 3 rd chuck table has, for example, a disk-shaped porous plate (not shown).
The lower surface side of the porous plate is connected to a suction source (not shown) such as an injector via a flow path (not shown) formed inside the 3 rd chuck table. When the suction source is operated, a negative pressure is generated on the upper surface (holding surface) of the porous plate.
A rotation drive source (not shown) such as a motor is connected to a lower portion of the 3 rd chuck table. Further, a grinding unit 14 is provided above the 3 rd chuck table. The grinding unit 14 includes a spindle housing (not shown), and an elevating mechanism (not shown) for elevating and lowering the grinding unit 14 in the Z-axis direction is coupled to the spindle housing.
A part of the spindle 16 is rotatably housed in the spindle housing. A motor for driving the main shaft 16 is connected to one end of the main shaft 16. The spindle 16 has the other end projecting from the spindle housing, and a disc-shaped grinding wheel mounting seat 18 is fixed to the other end.
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 an annular grinding wheel base 22 made of a metal material such as aluminum or stainless steel.
The upper surface side of the grinding wheel base 22 is fixed to the grinding wheel mounting base 18, and the grinding wheel base 22 is mounted on the spindle 16. A plurality of grinding stones 24 are provided on the lower surface side of the grinding wheel base 22. The plurality of grinding stones 24 are annularly arranged in the circumferential direction of the lower surface of the grinding wheel base 22 so that gaps are provided between the adjacent grinding stones 24.
Each grinding stone 24 is formed by mixing abrasive grains such as diamond and cBN (cubic boron nitride) with a bonding material such as metal, ceramic, or resin, for example. However, the bonding material or abrasive grains are not limited and may be appropriately selected according to the specification of the grinding stone 24.
A plurality of openings (not shown) for supplying grinding water such as pure water to the grinding stones 24 are formed on the lower surface side of the grinding wheel base 22 and on the inner peripheral side of the plurality of grinding stones 24. Instead of providing an opening for supplying grinding water on the lower surface side of the grinding wheel base 22, a grinding water supply nozzle (not shown) may be provided above the 3 rd chuck table.
In the back side grinding step (S40), first, the front surface 11a side of the wafer 11 is sucked and held by the holding surface of the 3 rd chuck table through the protective tape 19. While the 3 rd chuck table is rotated at, for example, 10rpm and the grinding wheel 20 is rotated at 3000rpm in predetermined directions, the grinding wheel 20 is fed downward at a predetermined speed (for example, 0.6 μm/s) by the lifting mechanism.
Thus, the grinding stone 24 is pressed against the back surface 11b of the wafer 11 to grind the back surface 11b until the back surface 11b of the wafer 11 has a predetermined finish thickness. During grinding, grinding water is supplied to the grinding wheel 24 at a predetermined flow rate of, for example, 3.0L/min or more and 7.0L/min or less.
When stress is applied to the wafer 11 during grinding, cracks (not shown) progress toward the front surface 11a and the back surface 11b with the modified layer 21 as a division starting point. The cracks reach the front surface 11a and the back surface 11b of the wafer 11, and the wafer 11 is divided into a plurality of device chips 23 (see fig. 6).
Fig. 5 (B) is an overall view of the front surface 11a side of the wafer 11 after the back surface side grinding step (S40), and fig. 5 (C) is a partial enlarged view of the front surface 11a side of the wafer 11 after the back surface side grinding step (S40). Fig. 6 is a perspective view of the device chip 23. The device chip 23 has a recessed portion corresponding to a part of the sidewall of the non-through hole 17 at the quadrangle thereof.
In embodiment 1, since the non-through holes 17 are formed at the intersections in the hole forming step (S10), and the non-through holes 17 have a depth B that is deeper than the depth a corresponding to the finish thickness, the corners of the device chips 23 can be prevented from rubbing against each other in the back-side grinding step (S40).
Therefore, the corner portions of the device chip 23 can be prevented from being chipped. Further, defects generated at the corners of the device chip 23 can be prevented from progressing to the regions where the devices 15 (functional elements) are formed. This can improve the bending strength of the device chip 23, for example, compared to the case where the non-through hole 17 is not formed in the wafer 11.
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 1 st laser beam irradiation unit 10. In contrast, in an etching process using an expensive photomask or the like, the photomask needs to be provided according to the type of pattern formed on the wafer 11. Therefore, the present embodiment has an advantage that the design such as the position and shape of the non-through hole 17 can be flexibly changed as compared with the etching process.
In addition, since the non-through holes 17 are formed in the present embodiment, there is an advantage that the time required for the hole forming step (S10) can be shortened as compared with the case of forming through holes, for example. Next, embodiment 2 in which through holes are formed will be described.
In the hole forming step (S10) of embodiment 2, through holes penetrating from the front surface 11a to the back surface 11b of the wafer 11 are formed instead of the non-through holes 17. This aspect is different from embodiment 1. Otherwise, the same as embodiment 1.
Fig. 8 is a diagram showing the hole forming step (S10) of embodiment 2. Fig. 8 shows a resin tape 27 attached to the front surface 11a side and constituting a wafer unit.
In the hole forming step (S10) of embodiment 2, the water-soluble resin is also spin-coated over the entire front surface 11a side. Then, the 1 st laser beam L is irradiated to the intersection on the front surface 11a side by using the 1 st laser beam irradiation unit 101A through hole 25 is formed at the intersection.
When the through hole 25 is formed, the 1 st chuck table is moved in a spiral shape by the horizontal movement mechanism. At this time, for example, when the 1 st chuck table is moved at a slower processing feed speed than that of embodiment 1, the through-hole 25 can be formed in the wafer 11. In addition, the 1 st laser beam L may be set to the same processing feed speed as in embodiment 1, and then the 1 st laser beam L may be set to the same processing feed speed as in embodiment 11Is higher than embodiment 1.
After the through holes 25 are formed at all the intersections, the wafer unit is transported to a water-soluble resin coating and cleaning apparatus, and the wafer 11 is cleaned. Thus, the wafer 11 having the through-holes 25 formed at the respective intersections can be formed.
Next, embodiment 3 will be explained. Fig. 9 is a flowchart of the manufacturing method of embodiment 3. In embodiment 3, after the front protection step (S20) and the internal processing step (S30), a hole forming step (S35) is performed.
More specifically, after the internal processing step (S30), a circular resin tape (not shown) having a diameter larger than that of the wafer 11 is attached to the back surface 11b side, and an annular frame is attached to the outer peripheral portion of the resin tape. Then, the protective tape 19 joined to the front surface 11a side in the front surface protecting step (S20) is separated (back surface protecting step (S33)).
After the back surface protection step (S33), a hole forming step (S35) is performed in the same manner as the hole forming step (S10) of embodiment 1. Thereby, the non-through holes 17 are formed at the intersections of the lines to divide 13.
After the hole forming step (S35), the front surface 11a side is covered with the protective tape 19 again, and the resin tape joined to the rear surface 11b side is separated (an additional front surface protecting step (S37)).
After the additional front surface protection step (S37), the back surface side grinding step (S40) is performed in the same manner as in embodiment 1 to grind the wafer 11 to a finish thickness. In embodiment 3 as well, since the corners of the device chip 23 can be prevented from rubbing against each other in the back-side grinding step (S40), the occurrence of chipping of the corners of the device chip 23 can be prevented.
Next, embodiment 4 will be explained. In embodiment 4, through-holes 25 are formed in the hole forming step (S35) of embodiment 3, instead of non-through-holes 17, as in embodiment 2. This aspect is different from embodiment 3. Otherwise, the same as embodiment 3.
In embodiment 4 as well, since the corners of the device chip 23 can be prevented from rubbing against each other in the back-side grinding step (S40), the occurrence of chipping of the corners of the device chip 23 can be prevented. In addition, the structure, method, and the like of the above embodiments may be modified and implemented as appropriate without departing from the scope of the object of the present invention.

Claims (3)

1. A method for manufacturing a plurality of device chips by dividing a workpiece, on a front surface side, in which devices are formed in a plurality of regions defined by a plurality of planned dividing lines set in a lattice shape, into device chips along the planned dividing lines, and manufacturing the plurality of device chips from the workpiece,
the method for manufacturing the plurality of device chips comprises the following steps:
a hole forming step of irradiating the 1 st laser beam having a wavelength absorbed by the workpiece from the outside of the workpiece to the front surface side to form a hole deeper than a depth corresponding to a finished thickness of each device chip at an intersection where the plurality of planned dividing lines intersect;
a front surface protecting step of covering the front surface side of the workpiece with a protective member;
an internal processing step of irradiating the 2 nd laser beam from the back side along each line to form a region having a lower intensity than a region not irradiated with the 2 nd laser beam in the inside of the object, while positioning a converging point of the 2 nd laser beam having a wavelength transmitted through the object at a position inside the object, the position being located on the back side of the object with respect to a depth corresponding to the finish thickness; and
and a back side grinding step of grinding the back side of the workpiece until the workpiece has the finished thickness, and dividing the workpiece into a plurality of device chips.
2. The method of manufacturing a plurality of device chips of claim 1,
in the hole forming step, a non-through hole that does not penetrate from the front surface to the back surface is formed as the hole.
3. The method of manufacturing a plurality of device chips of claim 1,
in the hole forming step, a through hole penetrating from the front surface to the back surface is formed as the hole.
CN202010825811.0A 2019-08-23 2020-08-17 Method for manufacturing multiple device chips Pending CN112420608A (en)

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