JP6902186B2 - How to cut the material to be processed - Google Patents

Description

The present invention relates to a method for cutting a material to be processed.

The material to be processed such as SiC is generally cut mechanically using a wire saw or the like. However, processing using a wire saw or the like has a problem that the processing is performed at a low speed and the throughput is lowered.

In order to solve this problem, a modified region is formed inside by irradiating a pulsed laser beam along the planned cutting surface of the material to be processed, and the material to be processed is cut along the planned cutting surface. (See Patent Document 1). In the method described in Patent Document 1, the laser beam is relatively moved along a predetermined line in a state where the condensing point is aligned on the planned cutting surface inside the SiC material. In Patent Document 1, the planned cutting surface has an angle corresponding to the off angle with the c-plane of the SiC crystal, and the pitch between one irradiation point of the laser beam and the other irradiation point closest to the one irradiation point is 1 μm. It is said that c-plane cracking from the modified region preferably occurs when the range is less than 10 μm.

However, when the line-shaped modified regions were actually formed side by side as shown in Patent Document 1, cracks extending from the modified region along the c-plane were confirmed only in one line-shaped modified region. However, when two line-shaped modified regions were formed, cracks along the c-plane were confirmed between these modified regions.

Japanese Unexamined Patent Publication No. 2013-49161

By the way, when the normal of the planned cutting surface is formed at an angle corresponding to the off-angle with the normal of the predetermined low exponential surface, when the linear modified regions are formed side by side, the predetermined region occurs in the predetermined region. If the crack extending along the low exponential surface of the above extends to the planned processing region before laser machining, the crack will occur at a position deviated from the planned cutting plane by the off angle in this region. Then, when this region is laser-processed, the laser beam is easily absorbed at the position where the crack occurs, so that the modified region is formed at a position deviated from the planned cutting surface. By repeating this, the cracks initially generated may extend endlessly along the predetermined low exponential surface, and the finally obtained cut surface may be significantly deviated from the planned cut surface.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for cutting a material to be processed so that the finally obtained cut surface does not deviate significantly from the planned cut surface. is there.

In order to achieve the above object, in the present invention, after forming a modified region by absorbing laser light on the planned cutting surface of the material to be processed made of hexagonal SiC, the material to be processed is subjected to the planned cutting surface. A method of cutting a material to be processed, in which the normal of the planned cutting surface is at a predetermined angle with the normal of the c-plane of the material to be processed, and the distance between the laser beam irradiation lines. Between the crack suppressing processing step of arranging a plurality of line-shaped modified regions and the line-shaped modified regions formed in the crack suppressing processing step as the distance along the c-plane where the cracks do not extend. In addition, cutting of the material to be processed includes a crack promoting processing step of forming an additional line-shaped modified region as a distance between adjacent laser beam irradiation lines as a distance at which cracks extend along the c-plane. The method is provided.

In the above-mentioned processing method of the SiC material, the distance at which the cracks along the c-plane do not extend can be four times or more the width dimension of the modified region.

In the above-mentioned processing method of the SiC material, the distance at which the crack extends along the c-plane can be less than four times the width dimension of the modified region.

Further, in the present invention, the processing target material is cut along the planned cutting surface after the modified region is formed by absorbing the laser beam on the planned cutting surface of the processing target material. Therefore, the normal of the planned cutting surface forms a predetermined angle with the normal of the predetermined low exponential surface of the material to be processed, and the distance between the irradiation lines of the laser beam is along the predetermined low exponential surface. An additional line is provided between the crack suppressing processing step of arranging a plurality of line-shaped modified regions and the line-shaped modified regions formed in the crack suppressing processing step as the distance at which the cracks do not extend. A method for cutting a material to be processed, which comprises a crack promoting processing step of forming a modified region having a shape as a distance between adjacent laser beam irradiation lines as a distance at which cracks extend along a predetermined low exponential surface. Is provided.

According to the cutting method of the material to be processed of the present invention, the finally obtained cut surface does not deviate significantly from the planned cutting surface.

FIG. 1 is a schematic perspective explanatory view of a SiC material showing an embodiment of the present invention. FIG. 2 is a schematic explanatory view of the laser irradiation device. FIG. 3 is a partial plan view of the SiC material in a state where the pre-modified region is formed. FIG. 4 shows a modified example, and is a partial plan view of the SiC material in a state where the pre-modified region is formed. FIG. 5 is a partial plan view of the SiC material in a state where the additional modification region is formed. FIG. 6 shows a modified example, and is a partial plan view of the SiC material in a state where an additional modified region is formed. FIG. 7 is a partial cross-sectional view of the SiC material in a state where the pre-modified region is formed. FIG. 8 is a partial cross-sectional view of the SiC material in a state where an additional modified region is formed. FIG. 9 is a partial cross-sectional view of a SiC material showing a comparative example.

1, FIG. 2, FIG. 3, FIG. 5, FIG. 7, and FIG. 8 show an embodiment of the present invention, and FIG. 1 is a schematic perspective explanatory view of a SiC material.
As shown in FIG. 1, the SiC material 1 is formed into a cylindrical shape and is divided into a plurality of SiC substrates 210 by being cut at a predetermined cut surface 100. In this embodiment, the SiC material 1 is made of 6H type SiC and can have a diameter of, for example, 3 inches. Further, each of the divided SiC substrates 210 is used, for example, as a substrate for a semiconductor device.

Here, each planned cutting surface 100 forms an angle corresponding to the off angle with the c surface orthogonal to the c axis of the 6H type SiC. Therefore, by cutting the SiC material 1 along each planned cutting surface 100, it is possible to manufacture the SiC substrate 210 having a main surface having an angle corresponding to the off angle with the c surface. The off angle is, for example, about 4 °.

FIG. 2 is a schematic explanatory view of the laser irradiation device.
As shown in FIG. 2, the laser irradiation device 300 includes a laser oscillator 310 that pulse-oscillates a laser beam, a mirror 320 that changes the direction of the oscillated laser beam, an optical lens 330 that focuses the laser beam, and a laser beam. It includes a stage 340 that supports the SiC laminated body 1 to be irradiated. Although a particularly detailed optical system is not shown in FIG. 2, the laser irradiation device 300 is capable of adjusting the focal position, adjusting the beam shape, correcting aberrations, and the like. Further, the laser irradiation device 300 has a housing 350 that maintains the path of the laser beam in a vacuum state. In the present embodiment, the laser irradiation device 300 is used to irradiate the SiC material 1 of the 6H type SiC with a laser beam to form a modified region inside the SiC material 1 and cut the SiC material 1.

The pulse width and wavelength of the laser beam oscillated from the laser oscillator 310 can be arbitrarily selected. For example, the pulse width can be picoseconds and the wavelength range can be near infrared. The laser light emitted by the laser oscillator 310 is reflected by the mirror 320 to change the direction. A plurality of mirrors 320 are provided to change the direction of the laser beam. Further, the optical lens 330 is located above the stage 340 and focuses the laser beam incident on the SiC material 1.

The stage 340 moves in the x direction and / or the y direction by a moving means (not shown), and moves the SiC material 1 placed on the stage 340. Further, the stage 340 may be rotatable about the z direction. That is, the SiC material 1 can be moved relative to the laser beam, whereby a processed surface formed by the laser beam can be formed at a predetermined depth of the SiC material 1.

The laser light is particularly absorbed in the vicinity of the condensing point in the SiC material 1, which forms a modified region in the SiC material 1. In the present embodiment, by relatively moving the laser beam along a predetermined line, a modification pattern composed of a plurality of line-shaped modification regions is formed on each planned cutting surface 100. The direction in which the laser beam is relatively moved is not limited to a linear shape, and can be moved in a curved line, for example.

Further, in the present embodiment, a line-shaped modified region is formed by performing one-pulse shots at predetermined intervals along each planned cutting surface 100. Processing spots are formed in the portion where the one-pulse shot is performed, and examples of such processing spots include crack spots, melting processing spots, refractive index change spots, or a mixture of at least two of these.

When cutting the SiC material 1, first, the laser beam is adjusted so that a modified region is formed on the planned cutting surface 100 on one end side in the axial direction located on the incident side of the laser light, and the laser light is applied to the planned cutting surface 100. Is absorbed to form a modified pattern. At this time, it is preferable to polish the surface of the SiC material 1 on the incident side so that the incident of the laser beam into the SiC material 1 is not hindered.

FIG. 3 is a partial plan view of the SiC material in which the pre-modified region is formed.
In forming the modification pattern, first, as shown in FIG. 3, the pre-modification region 12 is formed along the laser beam irradiation line 10 by linearly moving the focusing point of the laser beam. The pre-modification region 12 is formed as a set of modification spots formed by a one-pulse shot of pulsed laser light. In the present embodiment, the interval between the one-pulse shots of the laser beam is set so that a part of the adjacent condensing points overlaps, and the irradiation line 10 of the laser beam is continuously formed. As shown in FIG. 4, the interval between the one-pulse shots of the laser beam can be set so that the adjacent condensing points do not overlap, and the irradiation line 11 of the laser beam can be made intermittent. The width dimension of each pre-modified region 12 is arbitrary, but can be, for example, 10 μm or more and 50 μm or less. In the present embodiment, a plurality of line-shaped pre-modification regions 12 are formed side by side with the distance between the laser beam irradiation lines 10 as the distance P1 at which cracks do not extend along the c-plane (crack suppression processing step). In the present embodiment, the arrangement direction of each prior modification region 12 is a direction substantially orthogonal to the off direction. The arrangement direction of each preceding modification region 12 is arbitrary, but for example, the angle formed by the arrangement direction of each preceding modification region 12 and the direction orthogonal to the off direction can be within 30 degrees. The distance P1 at which the cracks along the c-plane do not extend is, for example, four times or more the width dimension of each pre-modified region 12.

FIG. 5 is a partial plan view of the SiC material in a state where the additional modification region is formed.
Next, as shown in FIG. 5, the distance between the line-shaped additional modification regions 13 and the adjacent laser beam irradiation lines 10 is set between the advance modification regions 12 formed in the crack suppression processing step. It is formed as a distance P2 at which cracks along the surface extend (crack promotion processing step). The distance P2 at which the crack along the c-plane extends is, for example, less than four times the width dimension of each pre-modified region 12. In this embodiment, the additional modification region 13 is formed in the middle of the adjacent preceding modification regions 12. Similar to the preceding modification region 12, the additional modification region 13 is also formed as a set of modification spots formed by one-pulse shot of pulsed laser light. In the present embodiment, the interval between the one-pulse shots of the laser beam is set so that a part of the adjacent condensing points overlaps, and the irradiation line 10 of the laser beam is continuously formed. As shown in FIG. 6, the interval between the one-pulse shots of the laser beam can be set so that the adjacent condensing points do not overlap, and the irradiation line 11 of the laser beam can be made intermittent. The width dimension of each additional modification region 13 is arbitrary, but can be, for example, 10 μm or more and 50 μm or less.

Here, the extended state of the crack along the c-plane in the SiC material will be described with reference to FIGS. 7 and 8. FIG. 7 is a partial cross-sectional view of the SiC material in which the pre-modified region is formed, and FIG. 8 is a partial cross-sectional view of the SiC material in which the additional modified region is formed.
As shown in FIG. 7, in the state where each pre-modified region 12 is formed, cracks 110 are formed in the vicinity of each pre-modified region 12 in the direction along the c-plane starting from each pre-modified region 12. Absent. Each pre-modified region 12 is formed with predetermined dimensions in the depth direction (vertical direction of FIGS. 7 and 8). When the additional modification region 13 is formed from this state, as shown in FIG. 8, each advance modification region 12 and each additional modification region 13 are formed between each advance modification region 12 and each additional modification region 13. Cracks 110 are independently generated in the direction along the c-plane as a starting point. Each crack 110 is inclined by an off angle with respect to the planned cutting surface 100. Here, as shown in FIG. 8, each of the preceding modified regions 12 and each of the additional modified regions 13 has a depth dimension that can be reached by the crack 110 extending from the adjacent modified region along the c-plane. preferable. If the depth dimension of each pre-modified region 12 and each additional modified region 13 is short, the crack 110 extending along the c-plane may not be properly extended between the modified regions.

After forming each pre-modified region 12 and each additional modified region 13 on the planned cutting surface 100, the direction in which the other end side in the axial direction of the SiC material 1 is fixed and separated from the other end side in the axial direction on one end side in the axial direction. The SiC material 1 is cut by applying a force to. After the peeling, it is preferable that the surface of the peeled substrate 210 and the new surface of the SiC material 1 are flattened by polishing or the like. In the present embodiment, the planned cutting surface 100 is not parallel to the c-plane and the peeled surface is jagged, so it is preferable to make it flat.

After that, each pre-modified region 12 and each additional modified region are similarly formed and cut on the planned cutting surface 100 on one end side in the axial direction of the SiC material 1 from which the substrate 210 has been peeled off. In this way, a plurality of SiC substrates 210 can be obtained by sequentially cutting the SiC material 1 from the other end side in the axial direction on all the planned cutting surfaces 100.

As described above, according to the method for processing the SiC material of the present embodiment, the cracks 110 are independently generated in each of the prior modification regions 12 and the additional modification regions 13, and the modifications 110 adjacent to each other are formed. Since it is prevented from extending beyond the cut surface, the final cut surface does not deviate significantly from the planned cut surface 100.

On the other hand, when all the modified regions 412 are formed in the order of arrangement, as shown in FIG. 9A, the initially formed modified region 412 does not have a crack 410, but is adjacent to the modified region 412. While processing the region 412, cracks extending along the c-plane may extend to the region to be processed. In this region, cracks 110 are generated at positions deviated from the planned cutting surface 100 by the off angle, and when laser processing is performed on this region, laser light is easily absorbed at the positions where cracks 110 are generated. As shown in b), the modified region 412 is formed at a position deviated from the planned cutting surface 100. When the modified region 412 is continuously formed in this way, as shown in FIG. 9C, the initially generated crack 410 extends endlessly along the c-plane, and is finally obtained. The cut surface deviates significantly from the planned cut surface 100

The prior modified region 12 and the additional modified region 13 may have a curved shape as well as a linear shape as shown in FIGS. 3 to 6. For example, each pre-modified region and each additional modified region may be formed in a spiral shape or may be concentric circles at predetermined intervals.

Further, in the above embodiment, the 6H type SiC material 1 to which the present invention is applied is shown, but for example, other polytype hexagonal SiC materials such as 4H type, as well as non-hexagonal SiCs. The present invention can also be applied to materials. Furthermore, it can be applied to materials other than SiC, such as GaN, AlN, sapphire, and diamond. In short, the normal of the planned cutting surface may be at a predetermined angle with the normal of the predetermined low exponential surface of the material to be processed. For example, in the above-described embodiment, the planned cutting surface 100 is shown to have an angle corresponding to the off angle with the c-plane which is a low exponential plane, but is off from other low-exponential planes such as the a-plane and m-plane. It may be an angle of an angle.

Although the embodiments of the present invention have been described above, the embodiments described above do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

As described above, the cutting method of the material to be processed of the present invention is industrially useful because the finally obtained cut surface does not deviate significantly from the planned cutting surface.

1 SiC material 12 Preliminary modification area 13 Additional modification area 100 Planned cutting surface 110 Crack 210 SiC substrate 300 Laser irradiation device 310 Laser oscillator 320 Mirror 330 Optical lens 340 Stage 350 Housing 410 Crack 412 Modification area Along the P1 c plane Distance at which cracks do not extend Distance at which cracks extend along the P2c plane

Claims (3)

A method for cutting a material to be processed, which is formed by absorbing laser light on a planned cutting surface of a material to be processed made of hexagonal SiC to form a modified region, and then cutting the material to be processed along the planned cutting surface. And
The normal of the planned cutting surface forms a predetermined angle with the normal of the c surface of the material to be processed.
The crack suppression processing step of forming a plurality of line-shaped modified regions side by side by setting the distance between the laser beam irradiation lines as the distance at which the cracks along the c-plane do not extend.
A crack promoting processing step of forming an additional line-shaped modified region between the line-shaped modified regions formed in the crack suppressing processing step is included.
A method for cutting a material to be processed, wherein each of the modified regions is formed to a depth dimension in which cracks extending along the c-plane can be reached from the adjacent modified regions. The method for cutting a material to be processed according to claim 1, wherein the distance at which the cracks along the c-plane do not extend is four times or more the width dimension of the modified region. A method for cutting a material to be processed, in which a modified region is formed by absorbing a laser beam on a surface to be cut of the material to be processed, and then the material to be processed is cut along the surface to be cut.
The normal of the planned cutting surface forms a predetermined angle with the normal of a predetermined low exponential surface of the material to be processed.
A crack suppression processing step of forming a plurality of line-shaped modified regions side by side with the distance between the laser beam irradiation lines as the distance at which cracks do not extend along the predetermined low index plane.
A crack promoting processing step of forming an additional line-shaped modified region between the line-shaped modified regions formed in the crack suppressing processing step is included.
A method for cutting a material to be processed, wherein each of the modified regions is formed to a depth dimension in which cracks along the predetermined low exponential surface can be reached from the adjacent modified regions.

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