JP7353157B2 - Laser processing method - Google Patents

Description

The present invention relates to a laser processing method for processing a workpiece.

In order to form a workpiece into a desired shape, a laser processing method is known in which the workpiece is irradiated with a laser beam of a transparent wavelength to form a division starting point, and the workpiece is divided by applying an external force. (See Patent Document 1 and Patent Document 2).

Japanese Patent Application Publication No. 2005-129607 Patent No. 6151557

However, in the laser processing methods shown in Patent Documents 1 and 2, the workpiece has a lens-like curvature, or a bump-like curvature is placed on the planned processing line of the workpiece. If the laser beam is present on the top, the laser beam is refracted and it becomes difficult to form a division starting point at a desired position, resulting in a problem that division defects occur and quality deteriorates.

The present invention has been made in view of such problems, and an object thereof is to provide a laser processing method that can suppress division defects of a workpiece having a curvature.

In order to solve the above-mentioned problems and achieve the objects, the laser processing method of the present invention is a laser processing method for forming a workpiece having a curvature into a desired shape, the method comprising: a holder for holding the workpiece; a coating step of coating the workpiece with a material through which the laser beam passes so that the curved surface of the workpiece becomes flat after the holding step; a laser processing step of irradiating the material and the workpiece with a laser beam of a wavelength that is transparent from the side coated with the material through which the laser beam passes, and performing a predetermined laser processing on the workpiece; After the laser processing step, the method includes a dividing step of applying an external force to the workpiece to divide it.

The laser processing method may include, before or after the dividing step, a peeling step of peeling off a material coated on a curved surface of the workpiece from the workpiece.

In the laser processing method, in the laser processing step, a pore and an amorphous material surrounding the pore may be formed inside the workpiece.

The present invention has the effect of being able to suppress poor division of a workpiece having a curvature.

FIG. 1 is a perspective view showing a workpiece to be processed by the laser processing method according to the first embodiment. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is a flowchart showing the flow of the laser processing method according to the first embodiment. FIG. 4 is a side view, partially in section, showing the holding step of the laser processing method shown in FIG. FIG. 5 is a side view, partially in cross section, showing a state in which a liquid coating member is dropped onto one surface of a workpiece in the coating step of the laser processing method shown in FIG. FIG. 6 is a side view, partially in cross section, showing a state in which a pressing member is opposed to a coating member dropped onto one surface of a workpiece in the coating step of the laser processing method shown in FIG. FIG. 7 is a side view, partially in section, showing a state in which the liquid coating member on one surface of the workpiece is formed flat in the coating step of the laser processing method shown in FIG. FIG. 8 is a cross-sectional view illustrating the refractive index of the covering member and the workpiece shown in FIG. 7. FIG. 9 is a side view, partially in cross section, showing a state in which the laser beam irradiation unit is positioned at one end of the processing line in the laser processing step of the laser processing method shown in FIG. FIG. 10 is a side view, partially in section, showing a state in which the laser beam irradiation unit has been moved to a position opposite to the other end of the planned processing line shown in FIG. FIG. 11 is a sectional view showing section XI in FIG. 10. FIG. 12 is a perspective view schematically showing the configuration of a shield tunnel formed in the workpiece shown in FIG. 11. FIG. 13 is a cross-sectional view of the workpiece held in the expanding device in the dividing step of the laser processing method shown in FIG. FIG. 14 is a cross-sectional view of the workpiece divided along the planned processing line in the dividing step of the laser processing method shown in FIG. FIG. 15 is a cross-sectional view schematically showing the peeling step of the laser processing method shown in FIG. 3. 16 is a perspective view of the workpiece after the peeling step of the laser processing method shown in FIG. 3. FIG. FIG. 17 is a flowchart showing the flow of the laser processing method according to the second embodiment. FIG. 18 is a perspective view showing a workpiece to be processed by the laser processing method according to the third embodiment. FIG. 19 is a sectional view of a main part of the workpiece shown in FIG. 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Further, the constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Further, various omissions, substitutions, or changes in the configuration can be made without departing from the gist of the present invention.

[Embodiment 1]
A laser processing method according to Embodiment 1 of the present invention will be explained based on the drawings. First, the workpiece 1 to be processed by the laser processing method according to the first embodiment will be described. FIG. 1 is a perspective view showing a workpiece to be processed by the laser processing method according to the first embodiment. FIG. 2 is a sectional view taken along line II-II in FIG.

(Workpiece)
As shown in FIGS. 1 and 2, the workpiece 1 to be processed by the laser processing method according to the first embodiment has a curvature on both one surface 2 and the other surface 3 on the back side of the one surface 2. It is formed into a curved surface. That is, both surfaces 2 and 3 are surfaces having curvature. In the first embodiment, the workpiece 1 is a convex lens that is made of a light-transmitting material, has both surfaces 2 and 3 formed into convex curved surfaces, and has a circular planar shape. In the first embodiment, the workpiece 1 is made of glass and has a thickness of 300 μm or more and 1 mm or less. Furthermore, in the present invention, in a cross section passing through the centers of both surfaces 2 and 3 of workpiece 1, a straight line passing through the center of curvature of both surfaces 2 and 3 is defined as the axis 4 of workpiece 1 (FIGS. 1 and 3). (indicated by a dashed line in 2).

(Laser processing method)
The laser processing method according to the first embodiment is a method for forming the planar shape of the workpiece 1 into a desired shape. In the first embodiment, the laser processing method is a method of forming the planar shape of the workpiece 1 into a rectangular shape (in the first embodiment, a square), but in the present invention, the desired shape of the workpiece 1 is , not limited to rectangles. In the first embodiment, the laser processing method is a method of cutting the outer edge of the workpiece 1 along a processing planned line 5 shown by a straight dotted line in FIG. In the first embodiment, four scheduled processing lines 5 are set.

FIG. 3 is a flowchart showing the flow of the laser processing method according to the first embodiment. As shown in FIG. 3, the laser processing method according to the first embodiment includes a holding step ST1, a covering step ST2, a laser processing step ST3, a dividing step ST4, and a peeling step ST5. Next, each step of the laser processing method according to the first embodiment will be explained.

(holding step)
FIG. 4 is a side view, partially in section, showing the holding step of the laser processing method shown in FIG. The holding step ST1 is a step of holding the workpiece 1 on the holding table 10 (shown in FIG. 4).

In the first embodiment, the holding table 10 includes a disk-shaped table main body 11 whose outer diameter is larger than the diameter of the workpiece 1, and a ring-shaped holding member 13 provided at the outer edge of the table main body 11. The table main body 11 has an upper surface 12 formed flat along the horizontal direction. The holding member 13 has an inner and outer diameter smaller than the diameter of the workpiece 1, and is arranged on the upper surface 12 of the table body 11 at a position coaxial with the table body 11. Further, in the first embodiment, the cross-sectional shape of the holding member 13 is formed into a semicircle that is convex upward. In the first embodiment, in the holding step ST1, the outer edge of the other surface 3 of the workpiece 1 is placed on the holding member 13 of the holding table 10, and the axis 4 is perpendicular to the upper surface 12 and held. The workpiece 1 is held at a position coaxial with the table 10. In addition, in the present invention, the shape of the holding table 10 is not limited to that described in the first embodiment, and for example, the holding table 10 may be made of a material (such as sponge or gel) that changes its shape to follow the shape of the workpiece 1. It may also be a holding table or the like.

(Coating step)
FIG. 5 is a side view, partially in cross section, showing a state in which a liquid coating member is dropped onto one surface of a workpiece in the coating step of the laser processing method shown in FIG. FIG. 6 is a side view, partially in cross section, showing a state in which a pressing member is opposed to a coating member dropped onto one surface of a workpiece in the coating step of the laser processing method shown in FIG. FIG. 7 is a side view, partially in section, showing a state in which the liquid coating member on one surface of the workpiece is formed flat in the coating step of the laser processing method shown in FIG. FIG. 8 is a cross-sectional view illustrating the refractive index of the covering member and the workpiece shown in FIG. 7.

In the coating step ST2, after the holding step ST1, a laser beam 20 (as shown in FIG. 8) is applied so that one surface 2 having curvature of the workpiece 1 (as shown in FIGS. 5, 6 and 7) becomes flat. ) is a step of covering with a covering member 30 which is a transparent material. In the coating step ST2, after positioning the coating nozzle 31 on one surface 2 of the workpiece 1, as shown in FIG. 5, the liquid coating member 30 is dripped from the coating nozzle 31, and as shown in FIG. Next, one surface 2 is entirely covered with a covering member 30.

The coating member 30 is cured when irradiated with ultraviolet rays, and at least has translucency after curing and emits a laser beam 20 having a wavelength (1030 nm in the first embodiment) that is transparent to the workpiece 1. It is transparent. That is, the laser beam 20 has a wavelength that is transparent to the coating member 30 and the workpiece 1 after being cured. Note that the dropped coating member 30 covers the entire surface 2 of one side of the workpiece 1 due to surface tension, as shown in FIGS. 5 and 6. Furthermore, in the present invention, even if the covering member 30 does not cover the entire surface 2 of the workpiece 1 at the time of dropping, the covering member 30 can be spread out by the pressing member 32 shown in FIG. The entire surface 2 of one side may be covered. In the first embodiment, the covering member 30 is Templock (registered trademark) manufactured by Denka Corporation, but the present invention is not limited thereto.

In the covering step ST2, when the dropped covering member 30 covers the entire one surface 2 of the workpiece 1, the pressing member 32 is positioned on the one surface 2 via the covering member 30, as shown in FIG. . The pressing member 32 has a flat lower surface 33 that faces one surface 2 with the covering member 30 in between. It is orthogonal to In the covering step ST2, the pressing member 32 is lowered and the lower surface 33 is pressed against the covering member 30, so that the upper surface 34 of the covering member 30 is formed flat as shown in FIG. Note that in the present invention, the liquid covering member 30 has a predetermined viscosity. The predetermined viscosity is a viscosity that can prevent the liquid coating member 30 from dripping from the top of the workpiece 1 due to dripping or pressing. This is because if it hangs down from above, it will not be possible to form a flat surface. In the coating step ST2, the coating member 30 is irradiated with ultraviolet rays to cure the coating member 30 with the upper surface 34 flat. Note that in the first embodiment, the upper surface 34 of the covering member 30 is perpendicular to the axis 4.

Further, in the present invention, the refractive index (absolute refractive index) of the coating member 30 after curing is equivalent to the refractive index (absolute refractive index) of the workpiece 1. The refractive index of the coating member 30 after curing is equivalent to the refractive index of the workpiece 1 means that, as shown in FIG. The focal point 21 of the laser beam 20 that passes through the workpiece 1 and converges into the workpiece 1 is focused on the laser beam 20 on the upper surface 34 in the horizontal direction (direction parallel to the upper surface 34 or perpendicular to the axis 4). It means to be located within the range 22 where the beam 20 is incident. Alternatively, in the present invention, the fact that the refractive index of the coating member 30 after curing is equivalent to the refractive index of the workpiece 1 means that the formation position (depth position) of the modified layer (modified region), etc. This means that it is within ±10 μm of the position. In addition, in Embodiment 1, both the refractive index of the coating member 30 and the refractive index of the workpiece 1 after curing are about 1.5.

(Laser processing step)
FIG. 9 is a side view, partially in cross section, showing a state in which the laser beam irradiation unit is positioned at one end of the processing line in the laser processing step of the laser processing method shown in FIG. FIG. 10 is a side view, partially in section, showing a state in which the laser beam irradiation unit has been moved to a position opposite to the other end of the planned processing line shown in FIG. FIG. 11 is a sectional view showing section XI in FIG. 10. FIG. 12 is a perspective view schematically showing the configuration of a shield tunnel formed in the workpiece shown in FIG. 11.

In the laser processing step ST3, after the coating step ST2, the laser beam 20 of the workpiece 1 is applied from the side covered with the coating member 30 with a laser beam having a wavelength that is transparent to the coating member 30 and the workpiece 1. In this step, the workpiece 1 is subjected to a predetermined laser processing by irradiating the laser beam 20. In the first embodiment, in the laser processing step ST3, the workpiece 1 is irradiated with the laser beam 20 shown in FIG. The workpiece 1 is processed to form a shield tunnel 40 shown in FIG.

In the first embodiment, in the laser processing step ST3, when irradiating the laser beam 20 along each planned processing line 5, the laser beam 20 is irradiated onto one end of the planned processing line 5, as shown in FIG. The laser beam irradiation unit 24 is positioned, and the focal point 21 of the laser beam 20 irradiated by the laser beam irradiation unit 24 is set within the workpiece 1. In the first embodiment, the laser beam irradiation unit 24 sets the condensing point 21 within the workpiece 1 and near the other surface 3, but it may also be set near the one surface 2. Further, if sufficient processing cannot be performed in the thickness direction of the workpiece 1 in one processing, processing may be performed multiple times by changing the light focusing position. Further, in the present invention, the laser beam irradiation unit 24 is provided with a spherical lens or a plurality of lenses, and the condensing point 21 is extended along the axis 4 inside the workpiece 1 to form a condensing area. It's okay.

In the first embodiment, in the laser processing step ST3, the workpiece 1 and the laser beam irradiation unit 24 are relatively moved along the processing line 5 while irradiating the pulsed laser beam 20 from the laser beam irradiation unit 24. Then, the laser beam irradiation unit 24 is moved toward the other end of the processing line 5. In the first embodiment, in the laser processing step ST3, as shown in FIG. 10, when the laser beam irradiation unit 24 is located on the other end of the processing line 5, the relative movement and irradiation of the laser beam 20.

In the first embodiment, in the laser processing step ST3, a shield having a pore 41 shown in FIGS. 11 and 12 and an amorphous material 42 surrounding the pore 41 is provided inside the workpiece 1 along the processing line 5. A plurality of tunnels 40 are formed. The pores 41 and the amorphous material 42 are formed across the upper surface 34 of the covering member 30 on which the laser beam 20 is incident from the other surface 3 side where the condensing point 21 of the laser beam 20 is positioned. The amorphous material 42 extends parallel to the axis 4 and penetrates the covering member 30 and the workpiece 1 between the upper surface 34 and the other surface 3 . It is formed around the pore 41 over the entire length. A plurality of shield tunnels 40 are formed along the processing line 5 at predetermined intervals.

In the first embodiment, as shown in FIG. 12, the inner diameter 411 of the pore 41 is about 1 μm, and the outer diameter 421 of the amorphous material 42 is about 5 μm. The interval between adjacent amorphous materials 42 is about 10 μm, and the amorphous materials 42 of adjacent shield tunnels 40 are connected to each other.

(split step)
FIG. 13 is a cross-sectional view of the workpiece held in the expanding device in the dividing step of the laser processing method shown in FIG. FIG. 14 is a cross-sectional view of the workpiece divided along the planned processing line in the dividing step of the laser processing method shown in FIG. The dividing step ST4 is a step of applying an external force to the workpiece 1 and dividing it along the processing line 5 after the laser processing step ST3.

In the first embodiment, in the dividing step ST4, the workpiece 1 is removed from the holding table 10, and the outer periphery of the disc-shaped adhesive tape 14 having a larger diameter than the workpiece 1 is attached to the annular frame 15. The upper surface 34 of the covering member 30 covering the workpiece 1 is attached to the center of the adhesive tape 14. In the dividing step ST4, the annular frame 15 is placed on the frame mounting plate 51 of the expanding device 50 via the adhesive tape 14, and the expanding device 50, as shown in FIG. Clamp the upper annular frame 15. At this time, in the first embodiment, the expanding device 50 positions the upper end of the expanding drum 53 on the same plane as the surface of the frame mounting plate 51, and brings the upper end of the expanding drum 53 into contact with the adhesive tape 14.

In the first embodiment, in the dividing step ST4, the expanding device 50 raises the expanding drum 53 using a lifting cylinder (not shown) to separate the annular frame 15 attached to the outer periphery of the adhesive tape 14, as shown in FIG. The workpiece 1 is moved relative to the workpiece 1 in the thickness direction. Then, since the upper end of the expansion drum 53 comes into contact with the adhesive tape 14, the adhesive tape 14 is expanded in the surface direction, and a radial tensile force, which is an external force, acts on the adhesive tape 14.

When a tensile force acts radially on the adhesive tape 14 attached to the upper surface 34 of the covering member 30 covering the workpiece 1, the tensile force also acts on the workpiece 1. Since shield tunnels 40 are formed at predetermined intervals along the processing line 5 in the laser processing step ST3, the workpiece 1 is fractured starting from the shield tunnels 40, as shown in FIG. Then, it is divided along the planned machining line 5. In addition, in the first embodiment, in the dividing step ST4, the expansion drum 53 is raised to expand the adhesive tape 14, but the present invention is not limited to this, and the frame mounting plate 51 may be lowered. In short, the expansion drum 53 may be raised relative to the frame mounting plate 51, and the frame mounting plate 51 may be lowered relative to the expansion drum 53.

(Peeling step)
FIG. 15 is a cross-sectional view schematically showing the peeling step of the laser processing method shown in FIG. 3. 16 is a perspective view of the workpiece after the peeling step of the laser processing method shown in FIG. 3. FIG. The peeling step ST5 is a step in which the covering member 30 coated on one surface 2 of the workpiece 1 is peeled off from the workpiece 1 after the dividing step ST4.

In the peeling step ST5, the workpiece 1 whose outer edge has been divided is picked up from the adhesive tape 14, and as shown in FIG. Soak in. Then, the covering member 30 is peeled off from one surface 2 of the workpiece 1. Note that in the present invention, the workpiece 1 is immersed in hot water 61 and the coating member 30 is peeled off, but in the present invention, the workpiece 1 may be immersed in a chemical solution and the coating member 30 is peeled off. After the coating member 30 is peeled off, it is taken out from the hot water tank 60 to obtain the workpiece 1 shown in FIG. 16 from which the outer edge has been removed.

As described above, in the laser processing method according to the first embodiment, in the covering step ST2, one surface 2 having a curvature of the workpiece 1 is covered with the covering member 30, and the upper surface 34 of the covering member 30 is made flat. Therefore, when irradiating the laser beam 20 in the laser processing step ST3, the condensing point 21 can be positioned at a desired position, and the shield tunnel 40, which is the starting point of division, can be formed at a desired position. As a result, the laser processing method according to the first embodiment can suppress the occurrence of defective division of the workpiece 1 and the deterioration of quality, and can suppress the defective division of the workpiece 1 having curvature on the surfaces 2 and 3. It has the effect of being able to do it.

Further, in the laser processing method according to the first embodiment, since the refractive index of the coating member 30 after curing is equal to the refractive index of the workpiece 1, the shield tunnel 40, which is the starting point of division, is formed at a desired position. be able to.

[Embodiment 2]
A laser processing method according to Embodiment 2 of the present invention will be explained based on the drawings. FIG. 17 is a flowchart showing the flow of the laser processing method according to the second embodiment. In addition, in FIG. 17, the same parts as in Embodiment 1 are denoted by the same reference numerals, and the description thereof will be omitted.

The laser processing method according to the second embodiment is the same as the first embodiment except that the peeling step ST5 is performed before the dividing step ST4. In the laser processing method according to the second embodiment, in the peeling step ST5, before the dividing step ST4, the coating member 30 coated on one surface 2 of the workpiece 1 is removed from the workpiece 1, as in the first embodiment. Peel it off.

In the laser processing method according to the second embodiment, in the coating step ST2, one surface 2 having a curvature of the workpiece 1 is coated with the coating member 30 to form the upper surface 34 of the coating member 30 flat. A certain shield tunnel 40 can be formed at a desired position, and similarly to the first embodiment, it is possible to suppress division defects of the workpiece 1 having curvature on the surfaces 2 and 3.

[Embodiment 3]
A laser processing method according to Embodiment 3 of the present invention will be explained based on the drawings. FIG. 18 is a perspective view showing a workpiece to be processed by the laser processing method according to the third embodiment. FIG. 19 is a sectional view of a main part of the workpiece shown in FIG. 18.

The laser processing method according to Embodiment 3 is the same as Embodiment 1 and Embodiment 2 except that the workpieces 1-3 to be processed are different.

The workpiece 1-3 to be processed in the laser processing method according to the third embodiment is a disk-shaped semiconductor wafer, an optical device wafer, etc. whose substrate 70 is silicon, sapphire, SiC (silicon carbide), gallium arsenide, or the like. It's a wafer. As shown in FIG. 18, the workpiece 1-3 has a device 73 formed in each region divided by a plurality of processing lines 72 formed in a grid pattern on the surface 71 of the substrate 70. The device 73 is an integrated circuit such as an IC (Integrated Circuit) or an LSI (Large Scale Integration). In the third embodiment, the workpiece 1-3 has a plurality of spherical bumps 74 mounted on the surface of a device 73, as shown in FIG. Bumps 74 protrude from the surface of device 73. The workpiece 1-3 has a curved surface having a curvature by mounting a spherical bump 74 on the surface of the device 73. When the workpiece 1-3 to be processed by the laser processing method according to the third embodiment has a surface having a curvature like a bump 74 near the planned processing line 72, the laser beam 20 is focused. In some cases, the bump 74 may be hit. As a result, the laser beam 20 is refracted, so that it may not be possible to process it to a desired position (depth).

In the laser processing method according to the third embodiment, in the coating step ST2, one surface 2 having a curvature of the workpiece 1 is coated with the coating member 30 to form the upper surface 34 of the coating member 30 flat. A certain shield tunnel 40 can be formed at a desired position, and similarly to the first embodiment, it is possible to suppress division defects of the workpiece 1 having curvature on the surfaces 2 and 3.

Note that the present invention is not limited to the above embodiments. That is, various modifications can be made without departing from the gist of the invention. In the embodiment, the shield tunnels 40 are formed at predetermined intervals along the processing line 5 as the predetermined laser processing, but the present invention is not limited to this, and the processing method is not limited to this. Processing may be performed to form a modified layer inside the workpiece 1 along the lines. Note that a modified layer refers to a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding area, and includes melt-treated regions, cracked regions, dielectric breakdown regions, Examples include a refractive index change region and a region in which these regions are mixed. The modified layer has lower mechanical strength than other parts of the workpiece 1.

Further, in the present invention, the structure of the holding member 13 is not limited to that described in the embodiment, but may be any structure as long as it can hold the other surface 3 side in the same manner as in the embodiment described above. Further, in the present invention, the expanding device 50 is not limited to expanding the adhesive tape 14, but may be a breaking device that divides the adhesive tape 14 along the processing line 5, for example.

1 Workpiece 2 One surface (surface with curvature)
3 Other surface (surface with curvature)
20 Laser beam 30 Covering member (material through which the laser beam passes)
41 Pore 42 Amorphous ST1 Holding step ST2 Coating step ST3 Laser processing step ST4 Dividing step ST5 Peeling step

Claims (3)

A laser processing method for forming a workpiece having a curvature into a desired shape, the method comprising:
a holding step of holding the workpiece;
After the holding step, a coating step of coating the workpiece with a material that is transparent to the laser beam so that the curved surface of the workpiece is flat;
After the coating step, the workpiece is irradiated with a laser beam having a wavelength that is transparent to the material and the workpiece from the side of the workpiece coated with the material through which the laser beam is transmitted. a laser processing step for performing predetermined laser processing on the
After the laser processing step, a dividing step of applying an external force to the workpiece to divide it;
A laser processing method characterized by comprising: 2. The laser processing method according to claim 1, further comprising a peeling step of peeling a material coated on a curved surface of the workpiece from the workpiece, before or after the dividing step. 3. The laser processing method according to claim 1, wherein in the laser processing step, a pore and an amorphous material surrounding the pore are formed inside the workpiece.

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