The present invention relates to a method for processing SiC material.
SiC materials are generally cut mechanically using a wire saw or the like. However, since SiC has high hardness, processing using a wire saw or the like has a problem that the processing is performed at a low speed and the throughput decreases.
In order to eliminate this problem, a SiC material cutting method in which a pulsed laser beam is irradiated along a cutting scheduled plane of a SiC material to form a altered region inside the SiC material and the SiC material is cut along the cutting scheduled plane is proposed (see Patent Document 1). In the method disclosed in Patent Document 1, the laser beam is moved in relation to the SiC material along a predetermined line in a state in which a focusing point is aligned on the cutting scheduled plane inside the SiC material. In Patent Document 1, it is described that a c-plane crack from the altered region is generated ideally when a pitch between one irradiation point of the laser beam and another irradiation point closes to the irradiation point is equal to or larger than 1 μm and smaller than 10 μm.
Patent Document 1: Japanese Patent Application Publication No. 2013-49161
However, when line-shaped altered regions are formed at equal intervals as illustrated in Patent Document 1, if the interval between respective lines exceeds a predetermined pitch, a crack does not progress between the respective lines. The pitch between respective lines may be set to be equal to or smaller than 10 μm as disclosed in Patent Document 1 in order to allow a crack to progress between respective lines reliably. However, in this case, it takes a considerable time to irradiate a laser beam to the cutting scheduled plane and the throughput decreases.
The present invention has been made in view of the above-described problem, and an object thereof is to provide a method for processing SiC material capable of allowing a crack to progress between respective lines reliably while shortening a laser beam irradiation time.
In order to attain the object, the present invention provides a method for processing SiC material, including: allowing a laser beam to be absorbed in a cutting scheduled plane of an SiC material to form an altered pattern including a plurality of line-shaped altered regions; and cutting the SiC material along the cutting scheduled plane, wherein the altered pattern has altered region groups including a plurality of line-shaped main altered regions extending in a predetermined direction and arranged at a first pitch, and a plurality of altered region groups is arranged at a second pitch larger than the first pitch.
In the method for processing SiC material, the altered pattern may include a plurality of line-shaped auxiliary altered regions extending in a different direction from the predetermined direction, and the auxiliary altered region may be formed so as to cross at least adjacent two altered region groups.
In the method for processing SiC material, the respective auxiliary altered regions may extend in a direction approximately orthogonal to the altered region group, wherein the respective auxiliary altered regions extend in a direction approximately orthogonal to the altered region group.
In the method for processing SiC material, the number of main altered regions included in one altered region group may be equal to or larger than 2 and equal to smaller than 10.
In the method for processing SiC material, the first pitch may be equal to or larger than 1.0 μm and smaller than 50 μm, and the second pitch may be equal to or larger than 50 μm and equal to smaller than 500 μm.
The present invention also provides a method fix processing SiC material including: allowing a laser beam to be absorbed in a cutting scheduled plane of an SiC material to form an altered pattern including a plurality of line-shaped altered regions; and cutting the SiC material along the cutting scheduled plane, wherein the altered pattern has a plurality of line-shaped main altered regions extending in a predetermined direction, and pitches between the respective main altered regions include at least two pitches.
According to the method for processing SiC material of the present invention, it is possible to allow a crack to progress between respective lines reliably while shortening a laser beam irradiation time.
As illustrated in
Here, the respective cutting scheduled planes 100 are at an angle corresponding to an off-angle with respect to the c-plane orthogonal to the c-axis of the 6H-SiC. Therefore, by cutting the SiC material 1 along the cutting scheduled plane 100, it is possible to manufacture the SiC substrate 210 having a circumferential surface that is at an angle corresponding to the off-angle with respect to the c-plane. The off-angle is approximately 4°, for example, and may be 0°. When the off-angle is 0°, the interface is parallel to the c-plane.
As illustrated in
The laser oscillator 310 can use second-order harmonics of a YAG laser. A beam emitted from the laser oscillator 310 is reflected by the mirror 320 whereby the direction is changed. A plurality of mirrors 320 is provided to change the direction of the laser beam. Moreover, the optical lens 330 is positioned above the stage 340 to focus the laser beam incident on the SiC material 1.
The stage 340 moves in x and/or y-directions with the aid of a moving mechanism (not illustrated) to move the SiC material 1 placed thereon. Furthermore, the stage 340 may rotate about the z-axis. That is, it is possible to move the SiC material 1 in relation to the laser beam. In this way, it is possible to form a surface machined by the laser beam at a predetermined depth of the SiC material 1.
The laser beam is absorbed at a portion inside the SiC material 1 particularly near the focusing point. As a result, an altered region is formed in the SiC material 1. In the present embodiment, the laser beam is moved in relation to the SiC material 1 along a predetermined line in a state in which the focusing point is aligned at the respective cutting scheduled planes 100 inside the SiC material 1 whereby an altered pattern formed of a plurality of line-shaped altered regions is formed in the respective cutting scheduled planes 100. The direction in which the laser beam is moved in relation to the SiC material is not limited to a line shape hut may be moved in a curve shape.
In the present embodiment, one shot of pulse is irradiated at predetermined intervals along the respective cutting scheduled planes 100 to form a line-shaped altered region. A machined spot is formed in a portion irradiated with one shot of pulse, and an example of such a machined spot includes a crack spot, a molten spot, a refractive index-altered spot, or a spot in which at least two of these spots are mixed.
When the SiC material 1 is cut, first, a focusing point of the laser beam is aligned on the cutting scheduled plane 100 on one end side in the axial direction positioned close to an incidence side of the laser beam so that the laser beam is absorbed. in the cutting scheduled plane 100 to form an altered pattern. In this case, it is preferable to polish an incidence-side surface of the SiC material 1 so that incidence of the laser beam on the SiC material 1 is not interrupted.
Specifically, as illustrated in
Here, when the SiC material 1 is processed, the respective main altered regions 12 are sequentially formed unless all main altered regions 12 are formed simultaneously. In this case, it is preferable to prevent a c-plane crack from progressing in a forming scheduled portion of a predetermined main altered region 12 as a result of forming of another main altered region 12 before the predetermined main altered region 12 is formed. If the c-plane crack progresses before laser processing is performed, it is difficult to align the focal point of laser at the depth of the cutting scheduled plane 100 and the processing accuracy decreases.
After the respective main altered regions 12 are formed in the cutting scheduled plane 100, the other end side in the axial direction of the SiC material 1 is fixed and force is applied in a direction from the other end side in the axial direction toward one end side in the axial direction whereby the SiC material 1 is cut. After the SiC material 1 is separated, it is preferable to planarize the surface of the separated substrate 210 and a new surface of the SiC material 1 by polishing or the like. Particularly, when the cutting scheduled plane 100 is not parallel to the c-plane, since the separation surface is rough, it is more preferable to planarize the separation surface.
After that, the main altered region 12 is formed in the cutting scheduled plane 100 on one end side in the axial direction of the SiC material 1 from which the substrate 210 is separated, and the SiC material 1 is cut. In this manner, the SiC material 1 is sequentially cut from the other end side of all cutting scheduled planes 100 whereby a plurality of SiC substrates 210 is obtained.
According to the above-described method for processing the SiC material 1, since the second pitch P2 of the respective altered region groups 13 is relatively large, it is possible to shorten the laser beam irradiation time during processing of the cutting scheduled plane 100.
Since the c-plane crack is made easy to progress, it is possible to reduce the power of laser for forming the altered regions and to reduce processing damage per one altered region. In this way, no excessive processing damage is applied to a region other than the cutting scheduled plane 100 in relation to the depth direction of the SiC material 1, the processing damage near the cutting scheduled plane 100 can be suppressed as much as possible, and the laser processing controllability is improved. Furthermore, since the altered region group 13 includes a plurality of main altered regions 12, it is possible to apply stress to the SiC material 1, the stress having a value relatively close to a threshold stress at which a c-plane crack occurs in the SiC material 1. In this way, the laser processing controllability is also improved.
The main altered region 12 may have a curve shape other than the line shape as illustrated in
In the embodiment, although the main altered regions 13 are formed at the first and second pitches P1 and P2, the main altered regions may be formed at three or more pitches. In this case, it is sufficient that the main altered regions 13 are formed at least at two pitches.
In the embodiment, although a plurality of main altered regions 12 extending in the same direction are formed, a plurality of line-shaped auxiliary altered regions 22 extending in a different direction from the main altered region 12 may be formed as illustrated in
As illustrated in
As illustrated in
In the embodiment, although the present invention is applied to the SiC material 1 formed of 6H-SiC, the present invention can be applied to other poly SiC materials such as 3C-SiC or 4H-SiC, for example. Furthermore, the present invention can be applied to materials other than SiC in which a progress direction of cracks in the material is approximately parallel to a cutting scheduled plane. Examples of such materials include GaN, AlN, ZnO, and the like. In the present embodiment, although a plane orientation in which a progress direction of cracks in the material is approximately parallel to a cutting scheduled plane is the c-plane, the plane orientation may be the m-plane or the a-plane.
Although the embodiment of the present invention has been described above, the invention according to the claims is not limited to the above-mentioned embodiment. Moreover, it should be noted that all combinations of the features described in the embodiment are not essential for solving the problem of the invention.
As described above, the method for processing SiC material according to the present invention is industrially useful in that it is possible to allow a crack to progress between respective lines reliably while shortening a laser beam irradiation time.
1: SiC material
11: Non-altered region
12: Main altered region
13: Altered region group
22: Auxiliary altered region
23: Auxiliary altered region group
100: Cutting scheduled plane
210: SiC substrate
300: Laser irradiation apparatus
310: Laser oscillator
320: Mirror
330: Optical lens
340: Stage
350: Housing
Number | Date | Country | Kind |
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2014-264140 | Dec 2014 | JP | national |
Filing Document | Filing Date | Country | Kind |
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PCT/JP2015/082171 | 11/16/2015 | WO | 00 |