WO2012096093A1 - Procédé d'usinage au laser - Google Patents

Procédé d'usinage au laser Download PDF

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Publication number
WO2012096093A1
WO2012096093A1 PCT/JP2011/079051 JP2011079051W WO2012096093A1 WO 2012096093 A1 WO2012096093 A1 WO 2012096093A1 JP 2011079051 W JP2011079051 W JP 2011079051W WO 2012096093 A1 WO2012096093 A1 WO 2012096093A1
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WO
WIPO (PCT)
Prior art keywords
sic substrate
modified region
along
cutting line
workpiece
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PCT/JP2011/079051
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English (en)
Japanese (ja)
Inventor
惇治 奥間
剛志 坂本
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浜松ホトニクス株式会社
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Publication of WO2012096093A1 publication Critical patent/WO2012096093A1/fr

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    • 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
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • 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
    • B23K26/0006—Working by laser beam, e.g. welding, cutting or boring taking account of the properties of the material involved
    • 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
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/083—Devices involving movement of the workpiece in at least one axial direction
    • B23K26/0853—Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
    • 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
    • B23K26/50—Working by transmitting the laser beam through or within the workpiece
    • B23K26/53—Working by transmitting the laser beam through or within the workpiece for modifying or reforming the material inside the workpiece, e.g. for producing break initiation cracks
    • 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
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/18—Sheet panels
    • 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
    • B23K2101/00—Articles made by soldering, welding or cutting
    • B23K2101/36—Electric or electronic devices
    • B23K2101/40—Semiconductor 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
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26

Definitions

  • the present invention relates to a laser processing method for cutting a plate-like workpiece including a SiC substrate along a planned cutting line.
  • SiC silicon carbide
  • a first modified region is formed in the SiC substrate along a first scheduled cutting line extending in a direction parallel to the main surface and the a-plane, and extends in a direction parallel to the main surface and the m-plane.
  • the second modified region is formed in the SiC substrate along the existing second cutting line, the cutting accuracy along the first cutting line is cut along the second cutting line. There is a possibility that it may deteriorate rather than accuracy. This is because cracks easily extend in the thickness direction of the SiC substrate from the second modified region, whereas cracks extend in the thickness direction of the SiC substrate from the first modified region. The present inventors have found that this is due to difficulties.
  • the present invention provides a laser processing method capable of accurately cutting a plate-like workpiece including a hexagonal SiC substrate having a principal surface that forms an angle corresponding to the c-plane and an off-angle along a planned cutting line.
  • the purpose is to provide.
  • a laser processing method provides a plate-like workpiece including a hexagonal SiC substrate having a main surface that forms an off-angle with respect to a c-plane in a direction parallel to the main surface and the a-plane.
  • a laser processing method for cutting along each of a first scheduled cutting line and a second scheduled cutting line extending in a direction parallel to the main surface and the m-plane, and focusing laser light By aligning the point with the inside of the SiC substrate and irradiating the workpiece with the laser beam along the first scheduled cutting line, the first modification that becomes the starting point of cutting along the first scheduled cutting line is performed.
  • a first step of forming a textured region inside the SiC substrate and after the first step, aligning the condensing point with the inside of the SiC substrate and emitting laser light along the second scheduled cutting line Cut along the second scheduled cutting line Comprising a second modified region to become a starting point and a second step of forming on the inside of the SiC substrate.
  • this laser processing method there is a condition for extending the crack in the thickness direction of the SiC substrate before forming the second modified region where the condition for extending the crack in the thickness direction of the SiC substrate is gentle.
  • a severe first modified region is formed.
  • a crack extends from the first modified region in the thickness direction of the SiC substrate at a portion where the first scheduled cutting line intersects the second scheduled cutting line. Can be prevented from being inhibited by the second modified region. Therefore, according to this laser processing method, it is possible to accurately cut a plate-like workpiece including a hexagonal SiC substrate having a main surface that forms an angle corresponding to the c-plane and an off-angle along a planned cutting line. It becomes possible.
  • the off angle includes the case of 0 °. In this case, the main surface is parallel to the c-plane.
  • the workpiece is cut along the first scheduled cutting line with the first modified region as a starting point, and the second modified region is formed.
  • the cutting along the second scheduled cutting line may be performed after the cutting along the first scheduled cutting line, or the first cutting may be performed after the cutting along the second scheduled cutting line.
  • Cutting along the planned cutting line may be performed.
  • the first modified region and the second modified region may include a melt processing region.
  • a plate-like workpiece including a hexagonal SiC substrate having a main surface that forms an angle corresponding to the c-plane and the off-angle can be accurately cut along a planned cutting line.
  • FIG. 3 is a cross-sectional view taken along the line III-III of the workpiece in FIG. 2. It is a top view of the processing target after laser processing.
  • FIG. 5 is a cross-sectional view taken along the line VV of the workpiece in FIG. 4.
  • FIG. 5 is a cross-sectional view taken along line VI-VI of the workpiece in FIG. 4.
  • the modified region is formed inside the processing object along the planned cutting line by irradiating the processing target with laser light along the planned cutting line.
  • a laser processing apparatus 100 includes a laser light source 101 that oscillates a laser beam L, a dichroic mirror 103 that is arranged so as to change the direction of the optical axis (optical path) of the laser beam L, and A condensing lens 105 for condensing the laser light L. Further, the laser processing apparatus 100 includes a support base 107 for supporting the workpiece 1 irradiated with the laser light L condensed by the condensing lens 105, and a stage 111 for moving the support base 107. And a laser light source control unit 102 for controlling the laser light source 101 to adjust the output of the laser light L, the pulse width, and the like, and a stage control unit 115 for controlling the movement of the stage 111.
  • the laser light L emitted from the laser light source 101 has its optical axis changed by 90 ° by the dichroic mirror 103, and the inside of the processing object 1 placed on the support base 107.
  • the light is condensed by the condensing lens 105.
  • the stage 111 is moved, and the workpiece 1 is moved relative to the laser beam L along the planned cutting line 5. As a result, a modified region along the planned cutting line 5 is formed on the workpiece 1.
  • a cutting target line 5 for cutting the processing object 1 is set in the processing object 1.
  • the planned cutting line 5 is a virtual line extending linearly.
  • the laser beam L is projected along the planned cutting line 5 in a state where the focused point P is aligned with the inside of the workpiece 1. It moves relatively (that is, in the direction of arrow A in FIG. 2).
  • the modified region 7 is formed inside the workpiece 1 along the planned cutting line 5, and the modified region 7 formed along the planned cutting line 5 is formed. It becomes the cutting start area 8.
  • the condensing point P is a location where the laser light L is condensed.
  • the planned cutting line 5 is not limited to a straight line, but may be a curved line, or may be a line actually drawn on the surface 3 of the workpiece 1 without being limited to a virtual line.
  • the modified region 7 may be formed continuously or intermittently. Further, the modified region 7 may be in the form of a line or a dot. In short, the modified region 7 only needs to be formed at least inside the workpiece 1.
  • a crack may be formed starting from the modified region 7, and the crack and modified region 7 may be exposed on the outer surface (front surface, back surface, or outer peripheral surface) of the workpiece 1.
  • the laser light L here passes through the workpiece 1 and is particularly absorbed near the condensing point inside the workpiece 1, thereby forming the modified region 7 in the workpiece 1. (Ie, internal absorption laser processing). Therefore, since the laser beam L is hardly absorbed by the surface 3 of the workpiece 1, the surface 3 of the workpiece 1 is not melted. In general, when a removed portion such as a hole or a groove is formed by being melted and removed from the front surface 3 (surface absorption laser processing), the processing region gradually proceeds from the front surface 3 side to the back surface side.
  • the modified region formed in the present embodiment refers to a region in which density, refractive index, mechanical strength, and other physical characteristics are different from the surroundings.
  • the modified region include a melt treatment region, a crack region, a dielectric breakdown region, a refractive index change region, and the like, and there is a region where these are mixed.
  • the modified region there are a region in which the density of the modified region in the material to be processed is changed as compared with the density of the non-modified region, and a region in which lattice defects are formed (collectively these are high-density regions). Also known as the metastatic region).
  • the area where the density of the melt treatment area, the refractive index change area, the modified area has changed compared to the density of the non-modified area, and the area where lattice defects are formed are further included in these areas and the modified areas.
  • cracks are included in the interface between the non-modified region and the non-modified region.
  • the included crack may be formed over the entire surface of the modified region, or may be formed in only a part or a plurality of parts.
  • the modified region 7 is formed by forming a plurality of modified spots (processing marks) along the planned cutting line 5.
  • the modified spot is a modified portion formed by one pulse shot of pulsed laser light (that is, one pulse of laser irradiation: laser shot).
  • Examples of the modified spot include a crack spot, a melting treatment spot, a refractive index change spot, or a mixture of at least one of these.
  • the size of the modified spot and the length of the crack to be generated are appropriately determined. It is preferable to control.
  • the workpiece 1 is a circular plate-shaped wafer (for example, a diameter of 3 inches and a thickness of 350 ⁇ m) including the SiC substrate 12.
  • SiC substrate 12 has a hexagonal crystal structure, and its crystal axis CA is inclined at an angle ⁇ (for example, 4 °) with respect to the thickness direction of SiC substrate 12. Yes. That is, SiC substrate 12 is a hexagonal SiC substrate having an off angle of angle ⁇ . As shown in FIG.
  • SiC substrate 12 has a front surface (main surface) 12a and a rear surface (main surface) 12b that form an angle ⁇ corresponding to the c-plane and the off angle.
  • the a plane is inclined at an angle ⁇ with respect to the thickness direction of the SiC substrate 12 (two-dot chain line in the figure), and the m plane is inclined with respect to the thickness direction of the SiC substrate 12. Not done.
  • the workpiece 1 includes a plurality of scheduled cutting lines (first scheduled cutting lines) 5 a extending in a direction parallel to the surfaces 12 a and a and a surface 12 a and A plurality of scheduled cutting lines (second scheduled cutting lines) 5m extending in a direction parallel to the m-plane are set in a lattice shape (for example, 1 mm ⁇ 1 mm).
  • Functional elements are formed on the front surface 12a of the SiC substrate 12 for each region defined by the planned cutting lines 5a and 5m, and the rear surface 12b of the SiC substrate 12 is a region defined by the planned cutting lines 5a and 5m.
  • a metal wiring is formed for each.
  • the functional element and the metal wiring constitute a power device in each chip obtained by cutting the workpiece 1 along the planned cutting lines 5a and 5m.
  • orientation flat 6a is formed in a direction parallel to planned cutting line 5a
  • orientation flat 6m is formed in a direction parallel to planned cutting line 5m.
  • the above workpiece 1 is cut along the scheduled cutting lines 5a and 5m as follows.
  • an expand tape 23 is attached to the workpiece 1 so as to cover the metal wiring on the back surface 12 b of the SiC substrate 12.
  • the condensing point P of the laser light L pulsated with a pulse width of 20 ns to 100 ns (more preferably with a pulse width of 50 ns to 60 ns) is set inside the SiC substrate 12.
  • the workpiece 1 is irradiated with the laser beam L along the planned cutting line 5a so that the pulse pitch is 10 ⁇ m to 18 ⁇ m (more preferably, the pulse pitch is 12 ⁇ m to 14 ⁇ m).
  • a modified region (first modified region) 7a serving as a starting point for cutting is formed inside SiC substrate 12 along planned cutting line 5a.
  • the modified region 7a includes a melt processing region.
  • the pulse pitch is a value obtained by dividing “the moving speed of the condensing point P of the laser beam L relative to the workpiece 1” by “the repetition frequency of the pulse laser beam L”.
  • the modified region 7a is formed with the surface 12a of the SiC substrate 12 as the laser light incident surface, the condensing point P of the laser light L being located inside the SiC substrate 12, and the collection along the planned cutting line 5a.
  • the light spot P is moved relatively.
  • the relative movement of the condensing point P along the scheduled cutting line 5a is performed a plurality of times (for example, 8 times) with respect to one scheduled cutting line 5.
  • a plurality of rows are arranged with respect to one scheduled cutting line 5a so as to be arranged in the thickness direction of the SiC substrate 12.
  • a number (for example, 8 rows) of modified regions 7a are formed.
  • the modified region 7a that is second closest to the surface 12a that is the laser light incident surface of the SiC substrate 12 is smaller than the modified region 7a that is closest to the surface 12a.
  • the modified region 7a is formed in order (that is, in order from the laser light incident surface). Note that the size of the modified region 7a can be adjusted by changing the pulse energy of the laser light L, for example.
  • cracks generated from the respective modified regions 7a extend in the thickness direction of the SiC substrate 12 and are connected to each other.
  • a crack extending in the thickness direction of the SiC substrate 12 from the modified region 7a closest to the surface 12a that is the laser light incident surface of the SiC substrate 12 is allowed to reach the surface 12a.
  • the laser beam is converged along the planned cutting line 5 m so that the condensing point P of the light L is aligned with the inside of the SiC substrate 12 so that the pulse pitch is 10 ⁇ m to 18 ⁇ m (more preferably, the pulse pitch is 12 ⁇ m to 14 ⁇ m).
  • the object L is irradiated with light L.
  • a modified region (second modified region) 7m serving as a starting point of cutting is formed inside SiC substrate 12 along planned cutting line 5m.
  • the modified region 7m includes a melt processing region.
  • the surface 12a of the SiC substrate 12 is used as the laser beam incident surface, the condensing point P of the laser beam L is located inside the SiC substrate 12, and the laser beam L is collected along the planned cutting line 5m.
  • the light spot P is moved relatively.
  • the relative movement of the condensing point P along the scheduled cutting line 5m is performed a plurality of times (for example, 6 times) with respect to one scheduled cutting line 5.
  • a plurality of columns are arranged with respect to one cutting scheduled line 5m so as to be arranged in the thickness direction of the SiC substrate 12.
  • the modified region 7m closest to the surface 12a which is the laser light incident surface of the SiC substrate 12 is smaller than the modified region 7m second closest to the surface 12a.
  • the modified region 7m is formed in order (that is, in order from the laser light incident surface). Note that the size of the modified region 7m can be adjusted by changing the pulse energy of the laser light L, for example.
  • each modified region 7m extends in the thickness direction of the SiC substrate 12 and is connected to each other.
  • a crack extending in the thickness direction of the SiC substrate 12 from the modified region 7m closest to the surface 12a that is the laser light incident surface of the SiC substrate 12 is allowed to reach the surface 12a.
  • the expanded tape 23 is expanded, and in this state, the back surface 12b of the SiC substrate 12 is passed through the expanded tape 23. Then, the knife edge 41 is pressed along each scheduled cutting line 5m. Thus, the workpiece 1 is cut into a bar shape along the planned cutting line 5m starting from the modified region 7m. At this time, since the expanded tape 23 is in an expanded state, the workpieces 1 cut into a bar shape are separated from each other as shown in FIG.
  • the back surface 12b of the SiC substrate 12 is passed through the expanded tape 23 with the expanded tape 23 continuously expanded as shown in FIG. 13 (a).
  • the knife edge 41 is pressed along each cutting planned line 5a.
  • the workpiece 1 is cut into chips along the scheduled cutting line 5a starting from the modified region 7a.
  • the expanded tape 23 is in an expanded state, the workpieces 1 cut into chips are separated from each other as shown in FIG. 13B. As described above, the workpiece 1 is cut into chips along the scheduled cutting lines 5a and 5m, and a large number of power devices are obtained.
  • the plate-like workpiece 1 including the hexagonal SiC substrate 12 having the surface 12a that forms an angle corresponding to the c-plane with respect to the c-plane is cut for the following reason.
  • 5m can be cut with high accuracy, and as a result, the workpiece 1 (that is, the power device) cut with high accuracy along the scheduled cutting lines 5a, 5m can be obtained.
  • the laser beam L is applied to the workpiece 1 along the scheduled cutting lines 5a and 5m so that the pulse pitch is 10 ⁇ m to 18 ⁇ m.
  • the cracks can be easily extended from the modified regions 7a and 7m in the thickness direction of the SiC substrate 12, while the modified regions 7a and 7m are c-planed.
  • the crack can be made difficult to extend in the direction.
  • the workpiece 1 is irradiated with the laser light L along the scheduled cutting lines 5a and 5m so that the pulse pitch becomes 12 ⁇ m to 14 ⁇ m, cracks are formed in the thickness direction of the SiC substrate 12 from the modified regions 7a and 7m. While making it easier to extend the crack, it is possible to make it difficult to extend the crack further from the modified regions 7a and 7m in the c-plane direction.
  • the laser beam L is oscillated with a pulse width of 20 ns to 100 ns.
  • the laser beam L is pulse-oscillated with a pulse width of 50 ns to 60 ns, cracks can be more reliably extended from the modified regions 7a and 7m in the thickness direction of the SiC substrate 12, while the modified region 7a. , It is possible to make it difficult to extend the crack more reliably in the c-plane direction from 7 m.
  • the modified region 7a that is second closest to the surface 12a that is the laser light incident surface of the SiC substrate 12 is formed relatively small. Thereby, even if the a-plane is inclined with respect to the thickness direction of the SiC substrate 12, the crack generated from the modified region 7a second closest to the surface 12a extends in the a-plane direction, and the line to be cut It is possible to prevent the surface 12a from being greatly deviated from 5a. Then, along the planned cutting line 5a, the modified region 7a closest to the surface 12a which is the laser light incident surface of the SiC substrate 12 is formed relatively large.
  • the crack is difficult to extend from the modified region 7a in the thickness direction of the SiC substrate 12, the crack can surely reach the surface 12a from the modified region 7a closest to the surface 12a.
  • a modified region 7m that is second closest to the surface 12a that is the laser light incident surface of the SiC substrate 12 is formed relatively large.
  • the modified region 7m closest to the surface 12a which is the laser light incident surface of the SiC substrate 12 is formed relatively small. Thereby, a crack can be reliably reached from the modified region 7m to the surface 12a while preventing the surface 12a from being damaged. As described above, the crack can surely reach the surface 12a from the modified region 7a along the planned cutting line 5a, and from the modified region 7m to the surface 12a along the planned cutting line 5m. The crack can be surely reached. This effect is exhibited regardless of the number of formation rows and the formation order of modified regions 7a and 7m, which will be described later, and is more remarkable when the number of formation rows and the formation order of modified regions 7a and 7m, which will be described later, are followed. .
  • the modified regions 7a having a larger number of columns are formed along the one scheduled cutting line 5a than in the case where the modified region 7m is formed along the one scheduled cutting line 5m.
  • the modified regions 7m having a smaller number of columns are formed along the single planned cutting line 5m than in the case where the modified region 7a is formed along the single planned cutting line 5a.
  • a crack can be greatly extended from the modified region 7m in the thickness direction of the SiC substrate 12 when each modified region 7m is formed.
  • the crack can be extended from the modified region 7a in the thickness direction of the SiC substrate 12 along the planned cutting line 5a, and the modified region 7m is formed along the planned cutting line 5m.
  • the crack can be extended in the thickness direction of the SiC substrate 12.
  • the condition for extending the crack in the thickness direction of the SiC substrate 12 is gentle, the condition for extending the crack in the thickness direction of the SiC substrate 12 is modified severely. Region 7a is formed. Thereby, when the modified region 7a is formed, the extension of the crack in the thickness direction of the SiC substrate 12 from the modified region 7a is inhibited by the modified region 7m at the portion where the planned cutting line 5a intersects the planned cutting line 5m. Can be prevented. This effect is exhibited regardless of the formation size and the number of formation rows of the modified regions 7a and 7m described above.
  • the workpiece 1 is cut along the planned cutting line 5m starting from the modified region 7m, and then the workpiece 1 is cut along the planned cutting line 5a starting from the modified region 7a.
  • the workpiece 1 is cut along the planned cutting line 5m, which is assumed to be relatively difficult to cut by forming the modified region 7m with a small number of rows, and then the modified region 7a with a large number of rows is formed.
  • the workpiece 1 is cut along the planned cutting line 5a that is assumed to be relatively easy to cut by the formation. Therefore, the force required to cut the workpiece 1 along the planned cutting line 5m and the force required to cut the workpiece 1 along the planned cutting line 5a are equalized, and the cutting target line 5m is aligned. Both the cutting accuracy and the cutting accuracy along the planned cutting line 5a can be further improved. This effect is exhibited regardless of the formation size and the number of formation rows of the modified regions 7a and 7m described above.
  • FIG. 14 is a view showing a photograph of a cut surface of the SiC substrate 12 cut along the planned cutting line 5a by the laser processing method described above.
  • FIG. 15 is a view showing a photograph of the cut surface of SiC substrate 12 cut along the planned cutting line 5m by the laser processing method described above.
  • FIG. 16 is a view showing a plan photograph of the SiC substrate 12 cut along the scheduled cutting lines 5a and 5m by the laser processing method described above.
  • a hexagonal SiC substrate 12 having a thickness of 350 ⁇ m and an off angle of 4 ° was prepared.
  • modified regions 7a were formed along one planned cutting line 5a along the planned cutting line 5a so as to be aligned in the thickness direction of the SiC substrate 12. Then, in order from the back surface 12b side of the SiC substrate 12, the modified region 7a that is second closest to the surface 12a that is the laser light incident surface of the SiC substrate 12 is smaller than the modified region 7a that is closest to the surface 12a. A modified region 7a was formed. From FIG. 14, it can be seen that the formation of the modified region 7a second closest to the surface 12a stops the extension of cracks generated from the modified region 7a. As a result, the meandering of the cut surface with respect to the planned cutting line 5a was suppressed to ⁇ 4 ⁇ m or less as shown in FIG.
  • the distance from the surface 12a to the position of the condensing point P is 314.5 ⁇ m, 280.0 ⁇ m, 246.0 ⁇ m, 212.0 ⁇ m, 171.5 ⁇ m in order from the modified region 7 a on the back surface 12 b side of the SiC substrate 12. 123.5 ⁇ m, 79.0 ⁇ m, 32.0 ⁇ m.
  • the pulse energy of the laser beam L is 25 ⁇ J, 25 ⁇ J, 25 ⁇ J, 25 ⁇ J, 25 ⁇ J, 20 ⁇ J, 15 ⁇ J, 6 ⁇ J, and 6 ⁇ J in order from the modified region 7 a on the back surface 12 b side of the SiC substrate 12.
  • modified regions 7 m were formed for one planned cutting line 5 m so as to be aligned in the thickness direction of the SiC substrate 12. Then, in order from the back surface 12b side of the SiC substrate 12, the modified region 7m closest to the surface 12a which is the laser light incident surface of the SiC substrate 12 is smaller than the modified region 7m second closest to the surface 12a. A modified region 7m was formed. From FIG. 15, it can be seen that the formation of the modified region 7m second closest to the surface 12a causes the cracks generated from the modified region 7m to extend to the surface 12a or the vicinity thereof. As a result, the meandering of the cut surface with respect to the planned cutting line 5m was suppressed to ⁇ 2 ⁇ m or less as shown in FIG.
  • the distance from the surface 12a to the position of the condensing point P is 315.5 ⁇ m, 264.5 ⁇ m, 213.5 ⁇ m, 155.0 ⁇ m, 95.5 ⁇ m in order from the modified region 7 m on the back surface 12 b side of the SiC substrate 12. 34.5 ⁇ m.
  • the pulse energy of the laser beam L is 25 ⁇ J, 25 ⁇ J, 20 ⁇ J, 20 ⁇ J, 15 ⁇ J, and 7 ⁇ J in order from the modified region 7 m on the back surface 12 b side of the SiC substrate 12.
  • cracks (hereinafter referred to as “half-cut”) reaching the surface 12a that is the laser light incident surface of the SiC substrate 12 from the modified regions 7a and 7m, and the modified regions 7a and 7m extend in the c-plane direction.
  • c-plane crack The relationship with a crack (hereinafter referred to as “c-plane crack”) will be described.
  • FIGS. 17 and 18 when the crack is to be extended in the thickness direction of the SiC substrate 12, half-cut is less likely to occur and c-plane cracks are generated compared to the modified region 7 m.
  • the modified region 7a that is more easily generated will be described as an object.
  • FIG. 19 is a table showing the relationship between the pulse width, the ID threshold value, the HC threshold value, and the machining margin.
  • the pulse width was changed in the range of 1 ns and 10 ns to 120 ns, and the ID threshold, HC threshold, and processing margin were evaluated for each pulse width.
  • FIG. 20 is a table showing the relationship between the pulse pitch, the ID threshold value, the HC threshold value, and the machining margin.
  • the pulse pitch was changed in the range of 6 ⁇ m to 22 ⁇ m, and the ID threshold value, the HC threshold value, and the machining margin were evaluated for each pulse pitch.
  • the ID threshold value is the minimum value of the pulse energy of the laser beam L that can cause c-plane cracking, and in order from the one with the highest ID threshold value (that is, the one that hardly causes c-plane cracking) Evaluated as acceptable or impossible.
  • the HC threshold value is the minimum value of the pulse energy of the laser beam L that can generate a half cut, and in order from the one having the lowest HC threshold value (that is, one that easily generates a half cut), excellent, good, acceptable, Rated as impossible.
  • the processing margin is a difference between the ID threshold value and the HC threshold value, and was evaluated as excellent, good, acceptable, or impossible in descending order of the processing margin. Then, the total was weighted in the priority order of ID threshold, HC threshold, and processing margin, and evaluated as excellent, good, acceptable, and impossible.
  • the SiC substrate 12 it is preferable to irradiate the SiC substrate 12 with the laser light L along the scheduled cutting lines 5a and 5m so that the pulse pitch becomes 10 ⁇ m to 18 ⁇ m, and the pulse pitch becomes 11 ⁇ m to 15 ⁇ m. It is more preferable to irradiate the SiC substrate 12 with the laser beam L along the scheduled cutting lines 5a and 5m, and further, the SiC substrate 12 along the scheduled cutting lines 5a and 5m so that the pulse pitch is 12 ⁇ m to 14 ⁇ m. It was found that it is even more preferable to irradiate with laser beam L.
  • production of a half cut can be accelerated
  • FIGS. 21 to 23 are tables showing experimental results of processing margins of the pulse width and the pulse pitch when the laser beam L is condensed with a numerical aperture of 0.8. These experimental results are the basis for the evaluation shown in FIGS.
  • the experimental conditions when the experimental results of FIGS. 21 to 23 are obtained are as follows. First, a condensing point of the laser beam L along the surface 12a and the planned cutting line 5a extending in a direction parallel to the a-plane, for a hexagonal SiC substrate 12 having a thickness of 4 ° and a thickness of 100 ⁇ m. P was moved. Further, the laser beam L was condensed with a numerical aperture of 0.8, and the condensing point P was set at a position of a distance of 59 ⁇ m from the surface 12 a which is the laser beam incident surface of the SiC substrate 12.
  • the energy (pulse energy) and power of the laser beam L and the pulse pitch of the laser beam L were respectively changed, and the modified region 7a, the half cut and the c-plane cracking state were observed.
  • the pulse width of the laser light L is 27 ns, 40 ns, and 57 ns
  • the pulse width (return frequency) of the laser light L is 10 kHz, 20 kHz, and 35 kHz.
  • the c-plane crack generation region is less than 150 ⁇ m with respect to the 40 mm region (20 mm ⁇ 2 regions).
  • LV1 was defined as LV2 when the c-plane crack generation region was less than 450 ⁇ m, and LV3 when the c-plane crack generation region was 450 ⁇ m or more.
  • the extension of c-crack in the direction perpendicular to the planned cutting line 5a is 10 ⁇ m to 20 ⁇ m
  • the extension of c-crack in the direction perpendicular to the planned cutting line 5a is the largest. It became about 100 ⁇ m.
  • FIG. 24 is a graph showing the relationship between the pulse pitch and the HC threshold.
  • FIG. 25 is a graph showing the relationship between the pulse pitch and the ID threshold value.
  • FIG. 26 is a graph showing the relationship between the pulse pitch and the machining margin.
  • the HC threshold is deteriorated (increased) by 2 ⁇ J from 15 ⁇ J to 17 ⁇ J, whereas the ID threshold is 17 ⁇ J to 29 ⁇ J. It is improved (increased) by 12 ⁇ J.
  • the pulse width of 40 ns a significant improvement in the processing margin was recognized in the range of the pulse pitch of 10 ⁇ m to 16 ⁇ m compared to the case of the pulse width of 27 ns.
  • the pulse width 57 ns a significant improvement in the processing margin was recognized in the range of the pulse pitch of 6 ⁇ m to 20 ⁇ m compared to the case of the pulse width 27 ns.
  • FIGS. 27 to 29 are tables showing experimental results of processing margins of the pulse width and pulse pitch when the laser beam L is condensed with a numerical aperture of 0.6. These experimental results are the basis for the evaluation shown in FIGS.
  • the experimental conditions when the experimental results of FIGS. 27 to 29 are obtained are as follows. First, a 350 ⁇ m-thick hexagonal SiC substrate 12 having a surface 12a that forms an off-angle with respect to the c-plane is targeted, along the surface 12a and the planned cutting line 5a extending in a direction parallel to the a-plane. The condensing point P of the laser beam L was moved. Further, the laser beam L was condensed with a numerical aperture of 0.6, and the condensing point P was aligned at a distance of 50 ⁇ m from the surface 12a which is the laser beam incident surface of the SiC substrate 12.
  • the energy (pulse energy) and power of the laser beam L and the pulse pitch of the laser beam L were respectively changed, and the modified region 7a, the half cut and the c-plane cracking state were observed.
  • the pulse width of the laser light L is 27 ns, 40 ns, and 57 ns
  • the pulse width (return frequency) of the laser light L is 10 kHz, 20 kHz, and 35 kHz.
  • ST indicates that a half cut has not occurred
  • HC indicates that a half cut has occurred
  • ID indicates that c-plane cracking has occurred
  • LV1 to LV3 indicate the scale of occurrence of c-plane cracking.
  • the criteria for LV1 to LV3 are the same as in the case of the experimental results shown in FIGS.
  • the modified region 7a also increases, and the violent crack caused by the OD greatly deviates from the planned cutting line 5a and reaches the surface 12a of the SiC substrate 12. Indicates. In this case, c-plane cracking was not evaluated. However, when the pulse width was 40 ns and the pulse width was 57 ns, large c-plane cracks did not occur at a pulse pitch of 12 ⁇ m or more.
  • FIG. 30 is a graph showing the relationship between the pulse pitch and the HC threshold. This graph is created based on the experimental results of FIGS. As shown in FIG. 30, when the pulse width is 57 ns, the HC threshold is less likely to be generated by about 2 ⁇ J to 4 ⁇ J than when the pulse width is 40 ns. Compared to the case of the numerical aperture 0.8 described above, when the numerical aperture is 0.6, the influence of the aberration is reduced at the condensing point P of the laser light L. Therefore, when the pulse width is 57 ns and when the pulse width is 40 ns. The HC threshold was similar. From this, it can be said that if the aberration is corrected, the HC threshold does not deteriorate even if the pulse width is large (up to at least 60 ns).
  • the experimental results of the processing margin of HC quality in the vicinity of the surface 12a that is the laser light incident surface of the SiC substrate 12 will be described.
  • the experimental conditions when the experimental results of FIGS. 31 to 33 are obtained are as follows. First, a condensing point of the laser beam L along the surface 12a and the planned cutting line 5a extending in a direction parallel to the a-plane, for a hexagonal SiC substrate 12 having a thickness of 4 ° and a thickness of 100 ⁇ m. P was moved. Further, the laser beam L was condensed with a numerical aperture of 0.8.
  • the laser beam L is irradiated with the pulse widths of 27 ns, 40 ns, 50 ns, and 57 ns, half-cut occurs at the focal point position 40.6 ⁇ m, and the focal point position 40.
  • the energy (pulse energy) at which the half cut does not occur at 6 ⁇ m the half cut state was observed by changing the focal point position in the range of 25.3 ⁇ m to 40.6 ⁇ m.
  • the pulse pitch of the laser beam L was constant at 14 ⁇ m.
  • the condensing point position is a distance from the surface 12a to the position of the condensing point P.
  • the laser beam L was irradiated with respective pulse widths of 27 ns, 40 ns, 50 ns, and 57 ns, and the half-cut state was observed by changing the pulse energy within the range of 7 ⁇ J to 12 ⁇ J.
  • the pulse pitch of the laser light L was constant at 14 ⁇ m, and the focal point position was constant at 34.5 ⁇ m.
  • half-cuts of the same quality were generated with the same pulse energy.
  • the laser beam L was irradiated at each pulse pitch of 10 ⁇ m, 12 ⁇ m, 14 ⁇ m, 16 ⁇ m, and 18 ⁇ m, and the half-cut state was observed by changing the pulse energy in the range of 7 ⁇ J to 12 ⁇ J. .
  • the pulse width of the laser beam L was fixed at 57 ns, and the focal point position was fixed at 34.5 ⁇ m. As a result, there was almost no change in the HC threshold due to the pulse pitch. Moreover, when the focal point position was 34.5 ⁇ m, the same quality of half-cut was generated with the same pulse energy.
  • a plate-like workpiece 1 including a hexagonal SiC substrate 12 having a surface 12a that forms an off-angle with the c-plane is prepared, and scheduled cutting lines 5a and 5m are set.
  • the workpiece 1 is irradiated with the laser beam L along each of the above.
  • a pre-modified region 7p is formed inside the SiC substrate 12 along each of the preliminary lines 5p.
  • This pre-modification region 7p includes a melt processing region.
  • the preliminary line 5p is a line that is located on both sides of the planned cutting line 5a (5m) in a plane parallel to the surface 12a and extends in a direction parallel to the planned cutting line 5a (5m).
  • the spare line 5p is a function adjacent to the SiC substrate 12 as viewed from the thickness direction. It is preferably set in the region between the elements.
  • a crack is generated in the SiC substrate 12 from the preliminary modified region 7p compared to the modified region 7a (7m) serving as a starting point of cutting. Make it difficult to do.
  • the pre-modified region 7p is less likely to cause a crack in the SiC substrate 12 than the modified region 7a (7m) that is the starting point of cutting by reducing the pulse energy, pulse pitch, pulse width, and the like of the laser light L. Can be.
  • the laser beam L is processed along the planned cutting line 5a (5m) by aligning the condensing point P of the laser beam L with the inside of the SiC substrate 12.
  • the object 1 is irradiated.
  • a modified region 7a (7m) serving as a starting point for cutting is formed inside the SiC substrate 12 along the planned cutting line 5a (5m).
  • the modified region 7a (7m) includes a melt processing region.
  • the plate-like workpiece 1 including the hexagonal SiC substrate 12 having the surface 12a that forms an angle corresponding to the c-plane with respect to the c-plane is cut for the following reason.
  • 5m can be cut with high accuracy, and as a result, the workpiece 1 (that is, the power device) cut with high accuracy along the scheduled cutting lines 5a, 5m can be obtained.
  • the preliminary modified region 7p is formed inside the SiC substrate 12 along each preliminary line 5p. Is formed.
  • the preliminary line 5p is located on both sides of the planned cutting line 5a (5m) in a plane parallel to the surface 12a and extends in a direction parallel to the planned cutting line 5a (5m). Therefore, even if a crack extends from the modified region 7a (7m) in the c-plane direction, as shown in FIG. 34B, as shown in FIG. 34B, the preliminary modified region 7p is not formed. Furthermore, the extension of the crack (c-plane crack) is suppressed by the pre-modified region 7p.
  • the crack extends from the modified region 7a (7m) in the thickness direction of the SiC substrate 12 without considering whether or not the crack easily extends in the c-plane direction from the modified region 7a (7m).
  • the workpiece 1 can be irradiated with laser light so as to be easy.
  • the pre-modified region 7p does not need to function as a starting point of cutting (that is, it promotes the extension of cracks from the pre-modified region 7p in the thickness direction of the SiC substrate 12). Since it is formed by the irradiation of the laser beam L so that the crack is hardly generated, it is possible to easily suppress the crack from extending from the pre-modified region 7p in the c-plane direction when the pre-modified region 7p is formed. . Accordingly, it is possible to accurately cut a plate-like workpiece including the hexagonal SiC substrate 12 having a main surface that forms an off-angle with the c-plane along the planned cutting line 5a (5m). .
  • the modified region 7a (7m) when the modified region 7a (7m) is formed, when the condensing point P of the laser beam L is set at a predetermined distance from the surface 12a that is the laser beam incident surface of the SiC substrate 12, the preliminary modified region 7p is formed. However, it is preferable to match the condensing point P of the laser beam L at the same distance from the surface 12a. According to this, the extension of the crack from the modified region 7a (7m) to the c-plane direction can be more reliably suppressed.
  • the SiC substrate along the planned cutting line 5a (5m) set between the preliminary lines 5p. Even if the modified region 7a (7m) is formed inside 12, the extension of c-plane cracking is suppressed by the pre-modified region 7p. In this case, it is preferable that the formation of the pre-modified region 7p along the preliminary line 5p precedes the formation of the modified region 7a (7m) along the planned cutting line 5a (5m).
  • a plate-like workpiece including a hexagonal SiC substrate having a main surface that forms an angle corresponding to the c-plane and the off-angle can be accurately cut along a planned cutting line.
  • SYMBOLS 1 DESCRIPTION OF SYMBOLS 1 ... Processing object, 5a, 5m ... Planned cutting line, 5p ... Preliminary line, 7a, 7m ... Modified region, 7p ... Pre-modified region, 12 ... SiC substrate, 12a ... Front surface (main surface), 12b ... Back surface (Main surface), L ... laser light, P ... condensing point.

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Abstract

Selon l'invention, est préparé un article à façonner (1) en forme de plaque et équipé d'un substrat SiC (12) à système hexagonal qui possède une surface (12a) constituée d'un angle d'une section angle de décalage avec une face (c). Ensuite, par irradiation à l'aide d'un faisceau laser (L), une région de modification (7a) est formée dans la partie interne du substrat SiC (12) le long d'une ligne de découpe prévue (5a) parallèle à la surface (12a) et à une face (a). Après formation de la région de modification (7a) de la ligne de découpe prévue (5a), par irradiation à l'aide d'un faisceau laser (L), une région de modification (7m) est formée dans la partie interne du substrat SiC (12) le long d'une ligne de découpe prévue (5m) parallèle à la surface (12a) et à une face (m).
PCT/JP2011/079051 2011-01-13 2011-12-15 Procédé d'usinage au laser WO2012096093A1 (fr)

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JP6399913B2 (ja) * 2014-12-04 2018-10-03 株式会社ディスコ ウエーハの生成方法
JP6358941B2 (ja) * 2014-12-04 2018-07-18 株式会社ディスコ ウエーハの生成方法
JP6563093B1 (ja) 2018-08-10 2019-08-21 ローム株式会社 ＳｉＣ半導体装置
US10576585B1 (en) 2018-12-29 2020-03-03 Cree, Inc. Laser-assisted method for parting crystalline material
US11024501B2 (en) 2018-12-29 2021-06-01 Cree, Inc. Carrier-assisted method for parting crystalline material along laser damage region
US10562130B1 (en) 2018-12-29 2020-02-18 Cree, Inc. Laser-assisted method for parting crystalline material
US10611052B1 (en) 2019-05-17 2020-04-07 Cree, Inc. Silicon carbide wafers with relaxed positive bow and related methods

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JP2009147108A (ja) * 2007-12-14 2009-07-02 Denso Corp 半導体チップ及びその製造方法
JP2009206221A (ja) * 2008-02-27 2009-09-10 Fuji Electric Device Technology Co Ltd 半導体装置の製造方法
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JP2010000542A (ja) * 2009-09-15 2010-01-07 Hamamatsu Photonics Kk レーザ加工方法、レーザ加工装置及びその製造方法

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