CN105810633B - Method for processing wafer - Google Patents
Method for processing wafer Download PDFInfo
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- CN105810633B CN105810633B CN201610021223.5A CN201610021223A CN105810633B CN 105810633 B CN105810633 B CN 105810633B CN 201610021223 A CN201610021223 A CN 201610021223A CN 105810633 B CN105810633 B CN 105810633B
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- 238000000034 method Methods 0.000 title claims abstract description 16
- 239000000758 substrate Substances 0.000 claims abstract description 23
- 230000001678 irradiating effect Effects 0.000 claims abstract description 13
- 238000005520 cutting process Methods 0.000 claims description 83
- 239000012212 insulator Substances 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- 239000002346 layers by function Substances 0.000 abstract description 49
- 238000003672 processing method Methods 0.000 abstract description 8
- 235000012431 wafers Nutrition 0.000 description 87
- 239000004065 semiconductor Substances 0.000 description 63
- 238000003384 imaging method Methods 0.000 description 20
- 230000000694 effects Effects 0.000 description 9
- 238000003754 machining Methods 0.000 description 7
- 230000010355 oscillation Effects 0.000 description 6
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 230000002093 peripheral effect Effects 0.000 description 4
- 229910052710 silicon Inorganic materials 0.000 description 4
- 239000010703 silicon Substances 0.000 description 4
- 230000001066 destructive effect Effects 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- 239000004642 Polyimide Substances 0.000 description 2
- 229910020177 SiOF Inorganic materials 0.000 description 2
- 239000006061 abrasive grain Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 229910003460 diamond Inorganic materials 0.000 description 2
- 239000010432 diamond Substances 0.000 description 2
- 238000005323 electroforming Methods 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229920000052 poly(p-xylylene) Polymers 0.000 description 2
- 229920001721 polyimide Polymers 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000008961 swelling Effects 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 229910002601 GaN Inorganic materials 0.000 description 1
- JMASRVWKEDWRBT-UHFFFAOYSA-N Gallium nitride Chemical compound [Ga]#N JMASRVWKEDWRBT-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 239000010445 mica Substances 0.000 description 1
- 229910052618 mica group Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920006254 polymer film Polymers 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
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Classifications
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28D—WORKING STONE OR STONE-LIKE MATERIALS
- B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
- B28D5/0005—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor by breaking, e.g. dicing
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B28—WORKING CEMENT, CLAY, OR STONE
- B28D—WORKING STONE OR STONE-LIKE MATERIALS
- B28D5/00—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor
- B28D5/0005—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor by breaking, e.g. dicing
- B28D5/0011—Fine working of gems, jewels, crystals, e.g. of semiconductor material; apparatus or devices therefor by breaking, e.g. dicing with preliminary treatment, e.g. weakening by scoring
Abstract
Provided is a method for processing a wafer in which devices are formed in a plurality of regions defined by a plurality of planned dividing lines formed in a lattice shape in a functional layer laminated on the front surface of a substrate, wherein the wafer can be divided along the planned dividing lines without peeling off the functional layer of the wafer and without generating voids, cracks, or the like in the substrate. The wafer processing method for forming devices in a plurality of regions defined by a plurality of planned dividing lines formed in a lattice shape in a functional layer laminated on a front surface of a substrate includes: a protrusion forming step of forming 2 protrusions by projecting the functional layer along the planned dividing lines by irradiating laser beams with a predetermined interval along the planned dividing lines formed on the wafer; and a dividing step of dividing the wafer subjected to the ridge forming step along the region sandwiched by the 2 ridges.
Description
Technical Field
The present invention relates to a method for processing a wafer in which a device is formed by a functional layer laminated on a front surface of a substrate such as silicon, and the wafer is divided along planned dividing lines.
Background
In a semiconductor device manufacturing process, a plurality of regions are defined by planned dividing lines arranged in a lattice pattern on a front surface of a semiconductor wafer having a substantially disk shape, and devices such as an IC and an LSI are formed on the defined regions. Then, the semiconductor wafer is cut along the lines to divide the region where the device is formed, thereby manufacturing each semiconductor device.
In recent years, in order to improve the throughput of semiconductor chips such as ICs and LSIs, semiconductor wafers of the following types have been put into practical use: in the semiconductor wafer, a silicon substrate or the like is laminated on the front surface thereof with SiO2And Low dielectric constant insulator coating films (Low-k films) composed of inorganic films such as SiOF and BSG (SiOB) and organic films such as polyimide and parylene polymer films.
The division along the lines to be divided of the semiconductor wafer is generally performed by a cutting device called a dicing saw. The cutting device comprises: a chuck table for holding a semiconductor wafer as a workpiece; a cutting mechanism for cutting the semiconductor wafer held on the chuck table; and a moving mechanism for moving the chuck table and the cutting mechanism relatively. The cutting mechanism includes a rotating spindle that rotates at high speed and a cutting tool mounted to the spindle. The cutting tool is composed of a disk-shaped base and an annular cutting edge attached to the outer periphery of the side surface of the base, and the cutting edge is formed by fixing diamond abrasive grains having a grain diameter of about 3 μm by electroforming, for example.
However, it is difficult to cut the Low-k film by a cutting tool. That is, since the Low-k film is very brittle like mica, there are the following problems: when cutting is performed along the planned dividing lines by a cutting tool, the Low-k film peels off, and the peeling reaches a circuit and causes fatal damage to the device.
In order to solve the above problem, patent document 1 below discloses a wafer dividing method including: the functional layer is removed by irradiating a laser beam having a wavelength that is absorptive for the functional layer along the planned dividing lines formed on the semiconductor wafer, and the semiconductor wafer is cut along the planned dividing lines by positioning a cutting tool in the laser processing groove and moving the cutting tool relative to the semiconductor crystal phase.
Patent document 1: japanese laid-open patent publication No. 2009-21476
However, when the functional layer is removed by irradiating laser light having a wavelength that is absorptive for the functional layer to form laser-processed grooves along the lines to be divided, there are the following problems: the laser beam from which the functional layer is removed is irradiated onto a semiconductor substrate such as a silicon substrate or a gallium nitride substrate, and a void, a crack, or the like is generated on the semiconductor substrate as a starting point of fracture, thereby lowering the flexural strength of the device.
Disclosure of Invention
The present invention has been made in view of the above circumstances, and a main technical object thereof is to provide a method for processing a wafer in which devices are formed in a plurality of regions defined by a plurality of planned dividing lines formed in a lattice shape on a functional layer laminated on a front surface of a substrate, and the wafer can be divided along the planned dividing lines without peeling off the functional layer of the wafer and without generating voids, cracks, or the like in the substrate.
In order to solve the above-described main technical problem, according to the present invention, there is provided a method of processing a wafer in which devices are formed in a plurality of regions defined by a plurality of planned dividing lines formed in a lattice shape in a functional layer laminated on a front surface of a substrate, the method comprising:
a protrusion forming step of forming 2 protrusions by projecting the functional layer along the planned dividing lines by irradiating the functional layer with laser beams at predetermined intervals along the planned dividing lines formed on the wafer; and
and a dividing step of dividing the wafer subjected to the ridge forming step along a region sandwiched by the 2 ridges.
In the ridge forming step, the output of the laser beam is set to an output that expands only the functional layer.
The output of the laser beam in the ridge forming step is set to 4nJ to 10nJ per 1 pulse of the laser beam.
In the ridge forming step, the interval between the spots of the laser beam is set to 4nm to 8 nm.
In the dividing step, the wafer is cut along the lines to be divided by positioning the cutting blade in the region sandwiched by the 2 ridges.
In the dividing step, the wafer is cut along the lines to be divided by irradiating the region sandwiched by the 2 ridges with a laser beam.
The method for processing a wafer according to the present invention includes the steps of: a protrusion forming step of forming 2 protrusions by projecting the functional layer along the planned dividing lines by irradiating laser beams at predetermined intervals along the planned dividing lines formed on the wafer; and a dividing step of dividing the wafer on which the ridge forming step is performed along a region sandwiched by the 2 ridges, so that the 2 ridges are formed on the functional layer constituting the wafer along the lines to be divided by performing the ridge forming step when the dividing step is performed, and hence the destructive force of the cutting tool or the irradiation of the laser beam is suppressed by the 2 ridges, so that the device side is not reached, the functional layer constituting the stacked device is not peeled off, and the quality of the device is not lowered.
Drawings
Fig. 1 is a perspective view and a main part enlarged cross-sectional view of a semiconductor wafer as a wafer processed by the wafer processing method of the present invention.
Fig. 2 is a perspective view showing a state in which the semiconductor wafer shown in fig. 1 is attached to the front surface of a dicing tape mounted on a ring-shaped frame.
Fig. 3 is a perspective view of a main part of a laser processing apparatus for performing a ridge forming step in the wafer processing method according to the present invention.
Fig. 4 is a block configuration diagram of a laser beam irradiation mechanism mounted on the laser processing apparatus shown in fig. 3.
Fig. 5 is an explanatory view of a ridge forming step in the wafer processing method of the present invention.
Fig. 6 is a block configuration diagram showing another embodiment of a condenser constituting a laser beam irradiation mechanism mounted on the laser processing apparatus shown in fig. 3.
Fig. 7 is a perspective view of a main part of a cutting apparatus for performing a cutting step as a dividing step in the wafer processing method according to the present invention.
Fig. 8 is an explanatory diagram of a cutting step as a dividing step in the wafer processing method of the present invention.
Fig. 9 is an explanatory diagram of a laser processing groove forming step as a dividing step in the wafer processing method of the present invention.
Description of the reference symbols
2: a semiconductor wafer; 3: a laser processing device; 31: a chuck table of a laser processing apparatus; 32: a laser beam irradiation mechanism; 324: a condenser; 33: a shooting mechanism; 4: a cutting device; 41: a chuck table of the cutting device; 42: a cutting mechanism; 423: a cutting tool; 43: a shooting mechanism; f: an annular frame; t: and scribing the tape.
Detailed Description
Hereinafter, preferred embodiments of the wafer processing method according to the present invention will be described in detail with reference to the drawings.
Fig. 1 (a) and (b) show a perspective view and a main part enlarged cross-sectional view of a semiconductor wafer as a wafer. In the semiconductor wafer 2 shown in fig. 1 (a) and (b), a functional layer 21 is formed on the front surface 20a of a substrate 20 of, for example, 100 μm thick, such as silicon, and an insulating film and a functional film forming a circuit are laminated on the functional layer 21, and a device 212 such as an IC or an LSI is formed on the functional layer 21 in a plurality of regions defined by a plurality of planned dividing lines 211 formed in a lattice shape. In the illustrated embodiment, the insulating film forming the functional layer 21 is formed of a Low dielectric constant insulator film (Low-k film) made of SiO2The film is composed of a film of inorganic substances such as SiOF and BSG (SiOB), or a film of polymers such as polyimide and parylene, i.e., an organic substance, and the thickness is set to 10 μm. The width of the line 211 is set to 50 μm in the illustrated embodiment.
To divide the semiconductor wafer 2 along the lines 211, a wafer supporting step is first performed in which a dicing tape is stuck to the back surface of the substrate 20 constituting the semiconductor wafer 2, and the outer peripheral portion of the dicing tape is supported by an annular frame. That is, as shown in fig. 2, the back surface 20b of the substrate 20 constituting the semiconductor wafer 2 is bonded to the front surface of the dicing tape T mounted so that the outer peripheral portion covers the inner opening of the annular frame F. Therefore, the front surface 21a of the functional layer 21 of the semiconductor wafer 2 bonded to the front surface of the dicing tape T is positioned above.
After the wafer supporting step described above is performed, a ridge forming step is performed to form 2 ridges by raising the functional layer 21 along the lines 211 to be divided by irradiating laser beams with a predetermined interval along the lines 211 to be divided formed in the semiconductor wafer 2. The ridge forming step is performed using the laser processing apparatus 3 shown in fig. 3. The laser processing apparatus 3 shown in fig. 3 includes: a chuck table 31 for holding a workpiece; a laser beam irradiation mechanism 32 for irradiating a laser beam on the workpiece held on the chuck table 31; and an imaging mechanism 33 for imaging the workpiece held on the chuck table 31. The chuck table 31 is configured to suck and hold a workpiece, and is moved in a machining feed direction (X-axis direction) indicated by an arrow X in fig. 3 by a machining feed mechanism (not shown), and is moved in an indexing feed direction (Y-axis direction) indicated by an arrow Y in fig. 3 by an indexing feed mechanism (not shown).
The laser beam irradiation mechanism 32 includes a cylindrical housing 321 extending substantially horizontally. The laser beam irradiation mechanism 32 will be described with reference to fig. 4.
The illustrated laser beam irradiation mechanism 32 includes: a pulsed laser beam oscillation mechanism 322 disposed in the housing 321; an output adjustment mechanism 323 that adjusts the output of the pulsed laser beam LB oscillated by the pulsed laser beam oscillation mechanism 322; and a condenser 324 for irradiating the workpiece W held on the holding surface of the chuck table 31 with the pulsed laser beam whose output is adjusted by the output adjusting mechanism 323.
The pulse laser beam oscillation mechanism 322 is composed of: a pulse laser beam oscillator 322a that oscillates a pulse laser beam; and a repetition frequency setting means 322b for setting the repetition frequency of the pulsed laser beam oscillated by the pulsed laser beam oscillator 322 a. In the illustrated embodiment, the pulse laser beam oscillator 322a oscillates a pulse laser beam LB having a wavelength of 355 nm.
The output adjusting means 323 adjusts the output of the pulsed laser beam oscillated from the pulsed laser beam oscillating means 322 to a predetermined output. The pulse laser beam oscillator 322a, repetition frequency setting means 322b, and output adjusting means 323 of the pulse laser beam oscillating means 322 are controlled by a control means not shown.
The condenser 324 includes: a direction conversion mirror 324a that converts the direction of the pulsed laser beam oscillated from the pulsed laser beam oscillation mechanism 322 and adjusted and output by the output adjustment mechanism 323 toward the holding surface of the chuck table 31; and a condenser lens 324b that condenses the pulse laser beam whose direction is converted by the direction conversion mirror 324a and irradiates the workpiece W held on the chuck table 31. The condenser 324 constructed in this manner is fitted to the front end of the housing 321 as shown in fig. 3.
Returning to fig. 3, the imaging mechanism 33 is attached to the distal end of the housing 321 constituting the laser beam irradiation mechanism 32. The imaging means 33 is composed of an optical system such as a microscope, an imaging device (CCD), and the like, and transmits an imaged image signal to a control means (not shown).
The ridge forming step is described with reference to fig. 3 and 4, and 2 ridges are formed by raising the functional layer 21 along the lines 211 to be divided by irradiating laser beams with the above-described laser processing apparatus at predetermined intervals along the lines 211 to be divided formed in the semiconductor wafer 2.
First, the wafer supporting step described above is performed, and the dicing tape T side of the semiconductor wafer 2 is placed on the chuck table 31. By operating a suction mechanism (not shown), the semiconductor wafer 2 is sucked and held on the chuck table 31 via the dicing tape T (wafer holding step). Therefore, the front surface 21a of the functional layer 21 of the semiconductor wafer 2 held on the chuck table 31 is positioned above. In fig. 3, the ring-shaped frame F to which the dicing tape T is attached is not shown, but the ring-shaped frame F is held by an appropriate frame holding mechanism disposed on the chuck table 31. In this way, the chuck table 31 which holds the semiconductor wafer 2 by suction is positioned directly below the imaging mechanism 33 by a not-shown processing and feeding mechanism.
When the chuck table 31 is positioned directly below the imaging mechanism 33, the alignment operation is performed, and the imaging mechanism 33 and a control mechanism, not shown, detect a processing region of the semiconductor wafer 2 to be laser-processed. That is, the imaging means 33 and a control means (not shown) perform image processing such as pattern matching for aligning the lines 211 to be divided, which are formed in a predetermined direction on the semiconductor wafer 2, with the condenser 324 of the laser beam irradiation means 32, and perform alignment of the laser beam irradiation positions (alignment step) in which the condenser 324 of the laser beam irradiation means 32 irradiates the laser beam along the lines 211 to be divided. The alignment of the laser beam irradiation position is similarly performed also on the lines to divide 211 formed in the direction perpendicular to the predetermined direction on the semiconductor wafer 2.
After the alignment step described above is performed, the chuck table 31 is moved to the laser beam irradiation region where the condenser 324 of the laser beam irradiation mechanism 32 for irradiating the laser beam is located as shown in fig. 3, and is positioned so that one end (left end in fig. 5 a) of the predetermined line to divide 211 formed in the semiconductor wafer 2 is positioned directly below the condenser 324 as shown in fig. 5 a. At this time, the position is located so that the position of 20 μm, for example, from the center of the line 211 to divide the image into two is directly below the condenser 324. The converging point P of the pulsed laser beam LB irradiated from the condenser 324 is positioned in the vicinity of the front surface (upper surface) of the functional layer 21 in the line to divide 211. Next, while the pulsed laser beam set to an output that expands only the functional layer 21 is irradiated from the condenser 324 of the laser beam irradiation mechanism 32, the chuck table 31 is moved in the direction indicated by the arrow X1 in fig. 5 (a) at a predetermined processing feed speed. As shown in fig. 5 b, after the other end (the right end in fig. 5 b) of the line 211 reaches a position directly below the condenser 324, the irradiation of the pulse laser beam is stopped, and the movement of the chuck table 31 is stopped.
Next, the chuck table 31 is moved by, for example, 40 μm in a direction perpendicular to the paper surface (index feeding direction). As a result, the position 20 μm from the center of the line 211 to the other side in the width direction is positioned directly below the condenser 324. Then, as shown in fig. 5 (c), while the pulsed laser beam is irradiated from the condenser 324 of the laser beam irradiation mechanism 32, the chuck table 31 is moved in the direction indicated by the arrow X2 at a predetermined processing feed speed, and after reaching the position shown in fig. 5 (a), the irradiation of the pulsed laser beam is stopped, and the movement of the chuck table 31 is stopped.
By performing the ridge forming step described above, 2 ridges 24 and 24 rising along the lines 211 to be divided are formed on the functional layer 21 of the semiconductor wafer 2 as shown in fig. 5 (d). The ridge forming step is performed along all the lines to divide 211 formed in the semiconductor wafer 2.
The ridge forming step is performed under the following processing conditions, for example.
Wavelength of laser light: 355nm
Repetition frequency: 80MHz
Average output: 0.5W
Diameter of the light-condensing spot:
processing feed speed: 450 mm/s
Next, another embodiment of the condenser 324 constituting the laser beam irradiation mechanism 32 of the laser processing apparatus 3 for performing the ridge forming step will be described with reference to fig. 6.
The condenser 324 shown in fig. 6 is provided with a branching means 324c such as a Wollaston prism (Wollaston prism) between the direction switching mirror 324a and the condenser lens 324b, and the branching means 324c branches the pulse laser beam whose direction has been switched by the direction switching mirror 324a in the Y-axis direction. The condenser 324 configured in this way irradiates the pulsed laser beams LB1 and LB2 branched by the branching mechanism 324c with a predetermined interval in the Y-axis direction. Therefore, by using the condenser 324 shown in fig. 6, 2 ridges rising along the line to divide can be formed at the same time. In the case of using the condenser 324 shown in fig. 6, since the outputs of the pulsed laser beams LB1 and LB2 branched by the branching means 324c are 1/2 of the output of the pulsed laser beam LB oscillated by the pulsed laser beam oscillation means 322, the average output of the pulsed laser beam LB oscillated by the pulsed laser beam oscillation means 322 in the ridge forming step is set to 1.0W.
After the ridge forming step described above, a dividing step is performed to divide the semiconductor wafer 2 along the region sandwiched by the 2 ridges 24, 24. Embodiment 1 of the dividing step is implemented in the illustrated embodiment by using a cutting apparatus 4 shown in fig. 7. The cutting device 4 shown in fig. 7 includes: a chuck table 41 for holding a workpiece; a cutting mechanism 42 for cutting the workpiece held on the chuck table 41; and an imaging mechanism 43 for imaging the workpiece held on the chuck table 41. The chuck table 41 is configured to suck and hold a workpiece, and is moved in a machining feed direction (X-axis direction) indicated by an arrow X in fig. 7 by a machining feed mechanism (not shown), and is moved in an indexing feed direction (Y-axis direction) indicated by an arrow Y by an indexing feed mechanism (not shown).
The cutting mechanism 42 includes a spindle housing 421 disposed substantially horizontally, a rotary spindle 422 rotatably supported by the spindle housing 421, and a cutting tool 423 attached to a tip end portion of the rotary spindle 422, and the rotary spindle 422 is rotated in a direction indicated by an arrow 423a by a servo motor, not shown, disposed in the spindle housing 421. Cutting insert 423 is comprised of the following components: a disk-shaped base 424 made of a metal material such as aluminum; and an annular cutting edge 425 attached to the outer peripheral portion of the side surface of the base 424. The annular cutting edge 425 is formed by an electroforming tool in which diamond abrasive grains having a grain size of 3 to 4 μm are fixed to the outer peripheral portion of the side surface of the base 424 by nickel plating, and in the illustrated embodiment, the annular cutting edge 425 is formed to have a thickness of 30 μm and an outer diameter of 50 mm.
The imaging mechanism 43 is attached to the front end of the spindle case 421, and includes: an illumination mechanism for illuminating the workpiece; an optical system that captures an area illuminated by the illumination mechanism; and an imaging device (CCD) for imaging an image captured by the optical system, and the imaging means 43 transmits an imaged image signal to a control means (not shown).
In order to perform the dividing step using the cutting apparatus 4, as shown in fig. 7, the dicing tape T side to which the semiconductor wafer 2 subjected to the ridge forming step is bonded is placed on the chuck table 41. Then, the semiconductor wafer 2 is sucked and held on the chuck table 41 via the dicing tape T by operating a suction mechanism (not shown) (wafer holding step). Therefore, the 2 convex stripes 24 and 24 formed along the lines 211 to divide of the semiconductor wafer 2 held on the chuck table 41 are located above. In fig. 7, the annular frame F to which the dicing tape T is attached is not shown, but the annular frame F is held by an appropriate frame holding mechanism disposed on the chuck table 41. In this way, the chuck table 41 which holds the semiconductor wafer 2 by suction is positioned directly below the imaging mechanism 43 by a not-shown processing and feeding mechanism.
When the chuck table 41 is positioned directly below the imaging mechanism 43, an alignment process is performed, and the imaging mechanism 43 and a control mechanism, not shown, detect a region of the semiconductor wafer 2 to be cut. In this alignment step, the 2 convex stripes 24 and 24 formed along the lines 211 to divide the semiconductor wafer 2 in the convex stripe forming step are imaged by the imaging mechanism 43. That is, the imaging mechanism 43 and a control mechanism (not shown) perform alignment as to whether or not the 2 convex stripes 24 and 24 formed along the planned dividing line 211 formed in the predetermined direction of the semiconductor wafer 2 are parallel to the processing feed direction (X-axis direction) (alignment step). If the 2 convex stripes 24, 24 formed along the planned dividing line 211 formed in the predetermined direction of the semiconductor wafer 2 are not parallel to the processing feed direction (X-axis direction), the chuck table 41 is rotated to adjust so that the 2 convex stripes 24, 24 are parallel to the processing feed direction (X-axis direction). The alignment of the cutting region cut by the cutting tool 423 is similarly performed also for the 2 convex strips 24, 24 formed in the direction perpendicular to the predetermined direction on the semiconductor wafer 2.
After the alignment of the cutting region is performed by detecting the 2 convex stripes 24 and 24 formed along the planned dividing lines 211 of the semiconductor wafer 2 held on the chuck table 41 in the above manner, the chuck table 41 holding the semiconductor wafer 2 is moved to the cutting start position of the cutting region. At this time, as shown in fig. 8 a, the semiconductor wafer 2 is positioned so that one end (left end in fig. 8 a) of the middle portion of the 2 convex strips 24, 24 formed along the planned dividing line 211 to be cut is positioned to the right side of the position directly below the cutting tool 423 by a predetermined amount.
After the semiconductor wafer 2 held on the chuck table 41 of the cutting apparatus 4 is positioned at the cutting start position in the cutting area in this way, the cutting tool 423 is plunged and fed downward as indicated by an arrow Z1 from the standby position indicated by a two-dot chain line in fig. 8 (a), and is positioned at a predetermined plunge and feed position as indicated by a solid line in fig. 8 (a). In the cutting feed position, as shown in fig. 8 (a) and 8 (c), the lower end of the cutting blade 423 is set at a position reaching the dicing tape T attached to the back surface of the semiconductor wafer 2.
Next, the cutting tool 423 is rotated at a predetermined rotational speed in a direction indicated by an arrow 423a in fig. 8 (a), and the chuck table 41 is moved at a predetermined cutting feed speed in a direction indicated by an arrow X1 in fig. 8 (a). As shown in fig. 8 b, in the chuck table 8, after the other end (the right end in fig. 8 b) of the middle portion of the 2 ridges 24, 24 is positioned a predetermined amount to the left side of the position directly below the cutting tool 423, the movement of the chuck table 41 is stopped. By performing the cutting feed to the chuck table 41 in this manner, as shown in fig. 8 (d), the substrate 20 of the semiconductor wafer 2 is cut with the cutting groove 25 formed, and the cutting groove 25 reaches the back surface of the region sandwiched by the 2 convex stripes 24, 24 formed in the line to divide 211 (cutting step).
Next, the cutting tool 423 is raised as indicated by an arrow Z2 in fig. 8 (b) to be positioned at a standby position indicated by a two-dot chain line, and the chuck table 41 is moved in a direction indicated by an arrow X2 in fig. 8 (b) to be returned to the position indicated in fig. 8 (a). Then, the chuck table 41 is indexed in a direction perpendicular to the paper surface (indexing direction) by an amount corresponding to the interval of the line to divide 211, and then the intermediate portions of the 2 convex stripes 24 and 24 formed along the line to divide 211 to be cut are positioned at positions corresponding to the cutting tool 423. In this way, the cutting process described above is performed after the intermediate portions of the 2 convex strips 24 and 24 formed along the next line 211 are positioned at the positions corresponding to the cutting tool 423.
The cutting step is performed under the following processing conditions, for example.
Cutting tool: an outer diameter of 50mm and a thickness of 30 μm
Rotational speed of cutting tool: 20000rpm
Cutting feed rate: 50 mm/sec
The cutting process described above is performed on the intermediate portions of the 2 convex stripes 24 and 24 formed along all the planned dividing lines 211 formed on the semiconductor wafer 2. As a result, the substrate 20 of the semiconductor wafer 2 is cut along the lines 211 to be divided, in which the 2 convex stripes 24 and 24 are formed, and is divided into the respective devices 212 (dividing step). When the dividing step is performed in this manner, since the 2 convex stripes 24 and 24 are formed on the functional layer 21 constituting the semiconductor wafer 2 along the lines to divide 211 by performing the convex stripe forming step, the destructive force of the cutting tool 423 is suppressed by the 2 convex stripes 24 and 24 so that the device 212 side is not reached, the functional layer 21 constituting the stacked devices is not peeled off, and the quality of the devices is not degraded.
Here, an experimental example will be described which relates to the effect of the 2 convex stripes 24 and 24 formed along the lines 211 to cut the functional layer 21 constituting the semiconductor wafer 2 on suppressing the peeling of the functional layer 21 by the cutting of the cutting blade 423.
[ Experimental example ]
[ Experimental example: 1]
The wavelength, repetition frequency, spot diameter, and feed rate of the laser beam in the processing conditions of the ridge forming step were fixed as described above, and 2 ridges 24 and 24 formed along the planned dividing line 211 were formed so that the average output became 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0W.
When the average output is 0.1W or 0.2W, no swelling of the functional layer is observed, and there is no effect of suppressing peeling of the functional layer 21 due to cutting along the lines 211 by the cutting tool.
When the average output is 0.3W, the functional layer protrusion of about 2 μm is observed, and there is an effect of suppressing the peeling of the functional layer 21 caused by the cutting along the lines 211 by the cutting tool.
When the average output is 0.4W to 0.7W, the functional layer is observed to bulge by 3 to 5 μm, and there is an effect of suppressing the peeling of the functional layer 21 by the cutting along the lines 211 by the cutting tool.
When the average output was 0.8W, the functional layer was broken, and the pulsed laser beam was irradiated onto the upper surface of the substrate to cause fine cracks. However, the effect of suppressing the peeling of the functional layer 21 by the cutting along the lines 211 by the cutting tool can be observed, and the reduction of the flexural strength of the device does not occur.
When the average output exceeds 0.9W, the swelling of the functional layer is broken, and the pulsed laser beam is irradiated to the upper surface of the substrate to generate voids and cracks. However, although the effect of suppressing the peeling of the functional layer 21 due to the cutting along the lines 211 by the cutting tool is observed, the flexural strength of the device is reduced.
Therefore, the energy per 1 pulse of the pulsed laser beam is preferably set to 0.3W/80MHz to 0.8W/80MHz, i.e., 4(3.75) nJ to 10 nJ.
[ Experimental example: 2]
The wavelength, repetition frequency, and spot diameter of the laser beam in the processing conditions of the ridge forming step were fixed as described above, and the processing feed rate was set to 260, 280, 300, 320, 340, 360, 380, 400, 420, 440, 460, 480, 500, 520, 540, 560, 580, 600, 620, 640, 660, 680, and 700 mm/sec, thereby forming 2 ridges 24 and 24 formed along the line to divide 211.
When the machining feed speed is 260 to 300 mm/sec, the 2 convex strips 24, 24 are locally broken, and although there is an effect of suppressing the peeling of the functional layer 21 during the cutting along the planned dividing lines 211 by the cutting tool, cracks are locally generated on the substrate, and the flexural strength of the device is lowered.
When the machining feed rate is 320 to 640 mm/sec, 2 good ridges 24, 24 are formed, and the effect of suppressing peeling of the functional layer 21 due to cutting along the planned dividing lines 211 by the cutting tool is exhibited.
When the machining feed rate exceeds 640 mm/sec, the 2 ridges 24, 24 are locally interrupted, and the effect of suppressing peeling of the functional layer 21 by cutting along the planned dividing line 211 by the cutting tool is local.
According to the above experimental results, the spot diameter at the irradiation spot isIn the case of the laser beam of (3), it is preferable that the processing feed rate is set to 320 to 640 mm/sec, and the interval between the laser beam spots is 4 to 8 nm. Therefore, the interval between the spots of the laser beam in the ridge forming step is preferably set to 4nm to 8 nm.
Next, embodiment 2 of the dividing step of dividing the semiconductor wafer 2 along the region sandwiched by the 2 convex stripes 24, 24 will be described with reference to fig. 9. Embodiment 2 of the dividing step is implemented using the laser processing apparatus 3 shown in fig. 3 and 4.
To perform the dividing step using the laser processing apparatus 3, from the state in which the ridge forming step is performed, as shown in fig. 9 (a), the chuck table 31 is moved to the laser beam irradiation region where the condenser 324 of the laser beam irradiation mechanism 32 that irradiates the laser beam is located, and is positioned so that one end (the left end in fig. 9 (a)) of the intermediate portion of the 2 ridges 24, 24 formed along the predetermined planned dividing line 211 formed on the semiconductor wafer 2 is located directly below the condenser 324. Next, while a pulse laser beam having a wavelength that is absorptive for the substrate 20 constituting the semiconductor wafer 2 is irradiated from the condenser 324 of the laser beam irradiation mechanism 32, the chuck table 31 is moved at a predetermined processing feed speed in the direction indicated by the arrow X1 in fig. 9 (a). As shown in fig. 9 b, after the other end (right end in fig. 9 b) of the intermediate portion of the 2 convex stripes 24, 24 formed along the planned dividing line 211 reaches the position directly below the condenser 324, the irradiation of the pulse laser beam is stopped, and the movement of the chuck table 61 is stopped.
By performing the above-described laser processing step, the substrate 20 constituting the semiconductor wafer 2 is cut by the laser processing groove 26 formed along the intermediate portion of the 2 convex stripes 24, the 2 convex stripes 24, 24 being formed along the lines to divide 211, as shown in fig. 9 (c) (laser processing groove forming step).
The laser groove forming step is performed under the following processing conditions, for example.
Wavelength of laser light: 355nm
Repetition frequency: 50MHz
Average output: 3W
Diameter of the light-condensing spot:
processing feed speed: 100 mm/sec
The above-described laser groove forming step is performed along the intermediate portions of the 2 convex strips 24, and the 2 convex strips 24, 24 are formed along all the lines to divide 211 formed in the semiconductor wafer 2, whereby the semiconductor wafer 2 is cut along the lines to divide 211 and is divided into the respective devices 212 (dividing step). When the dividing step is performed in this manner, since the 2 convex stripes 24 and 24 are formed on the functional layer 21 constituting the semiconductor wafer 2 along the lines to divide 211 by performing the convex stripe forming step, the destructive force of the laser beam is suppressed by the 2 convex stripes 24 and 24 so that the device 212 side is not reached, the functional layer 21 constituting the stacked devices is not peeled off, and the quality of the devices is not degraded.
Claims (5)
1. A method for processing a wafer having devices formed in a plurality of regions defined by a plurality of planned dividing lines formed in a lattice shape on a low dielectric constant insulating film laminated on a front surface of a substrate, the method comprising:
a protrusion forming step of forming 2 protrusions by projecting a low dielectric constant insulator coating film along planned dividing lines formed on a wafer by irradiating the wafer with laser beams at predetermined intervals along the planned dividing lines; and
a dividing step of dividing the wafer subjected to the ridge forming step along a region sandwiched by the 2 ridges,
in the ridge forming step, the point of convergence of the laser beam is positioned in the vicinity of the surface of the low dielectric constant insulator film at the planned dividing line, and the output of the laser beam is set to an output that expands only the low dielectric constant insulator film.
2. The method of processing a wafer according to claim 1,
the energy per 1 pulse of the laser beam is set to 4nJ to 10nJ with respect to the output of the laser beam in the ridge forming step.
3. The method of processing a wafer according to claim 2,
the interval between the spots of the laser beam in the ridge forming step is set to 4nm to 8 nm.
4. The method of processing a wafer according to any one of claims 1 to 3,
in the dividing step, the wafer is cut along the lines to be divided by positioning the cutting blade in the region sandwiched by the 2 ridges.
5. The method of processing a wafer according to any one of claims 1 to 3,
in the dividing step, the wafer is cut along the lines to be divided by irradiating the region sandwiched by the 2 ridges with a laser beam.
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