JP7377308B2 - Cutting method and tip - Google Patents

Description

The present invention relates to a cutting method and a chip.

β-Ga ₂ O ₃ crystal has a (100) plane as a cleavage plane with very strong cleavage. Therefore, the β-Ga ₂ O ₃ substrate has a property that cleavage tends to occur along the (100) plane when it is separated by blade dicing. Generally, in order to prevent the occurrence of cleavage, it is possible to reduce the cutting rate, but in order to prevent cleavage of the Ga ₂ O ₃ substrate, the cutting rate must be set to a very small value (for example, 0.1 mm/sec to 0.3 mm/sec), and the cutting process takes a very long time.

Furthermore, a method is conventionally known in which a modified region is formed inside a substrate using a laser beam to separate the substrate (see, for example, Patent Documents 1 and 2). The modified region is a region formed by moving the focal point of the laser beam along the planned cutting line of the substrate, and if the modified region is properly formed, an external force is applied to the substrate. This allows the substrate to be split along the planned cutting line.

Japanese Patent Application Publication No. 2008-68319 International Publication No. 2008/146744

However, when separating a substrate including a cleavage plane with strong cleavability, such as a Ga ₂ O ₃ -based substrate, even with the methods described in Patent Documents 1 and 2, it is necessary to apply external force for separation. In this case, cleavage may occur in a plane different from the desired plane.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cutting method and a chip capable of cutting a workpiece containing gallium oxide at high speed while suppressing the influence of cleavage.

A cutting method according to the present invention is a cutting method for cutting a workpiece containing gallium oxide along a line to be cut, which has a first surface and a second surface opposite to the first surface. A first step of forming a modified region on the workpiece along the line to be cut by irradiating the workpiece with a laser beam along the line to be cut with the surface as the incident surface of the laser beam; After that, a second step of cutting the workpiece along the scheduled cutting line by inserting a cutting tool into the workpiece along the scheduled cutting line; By forming a plurality of rows of modified regions on the line so as to intersect at least the line to be cut and arranged in a first direction along the first surface, modification including a plurality of rows of modified regions is performed. Forms mass part.

In this cutting method, the workpiece to be cut contains gallium oxide. Therefore, when cutting a workpiece by blade dicing as described above, it is necessary to reduce the cutting rate. Further, when applying an external force to the workpiece and cutting the workpiece starting from the modified region, the influence of the cleavage plane of gallium oxide is likely to occur. In contrast, in this cutting method, in the first step, a modified region is formed along the line to be cut, and in the second step, a cutting tool is inserted into the workpiece along the line to be cut. This cuts the workpiece. In this way, by performing cutting in a state that has become brittle due to the formation of modified regions (for example, the crystallinity of gallium oxide has decreased), it becomes possible to cut the workpiece while suppressing the effects of cleavage. . In particular, in the first step, a modified portion including a plurality of rows of modified regions is formed for one scheduled cutting line. Therefore, it becomes possible to cut the modified portion at high speed using a cutting tool having a certain width. Therefore, according to this cutting method, a workpiece containing gallium oxide can be cut at high speed while suppressing the influence of cleavage.

In the cutting method according to the present invention, in the first step, a plurality of rows of modified regions are formed with respect to one scheduled cutting line so as to be arranged in a second direction from the second surface to the first surface. A modified portion may be formed by this. In this case, since the modified portion extends in the thickness direction (second direction) of the workpiece, it is possible to cut at a higher speed while reliably suppressing the influence of cleavage.

In the cutting method according to the present invention, in the first step, a plurality of rows of modified regions are formed while maintaining the position of the focal point of the laser beam in the second direction. A modified portion including a plurality of modified layers may be formed by repeating the modified layer forming step of forming the layers while changing the position of the focal point of the laser beam in the second direction. In this way, if the modified part is configured by laminating modified layers along the thickness direction (second direction) of the workpiece, the shape and state of the modified part in the thickness direction can be controlled. It becomes easier.

In the cutting method according to the present invention, in the first step, the modified layer forming step is repeated while sequentially changing the position of the focal point of the laser beam in the second direction from the second surface side to the first surface side. Thus, a modified portion including a plurality of modified layers may be formed. In this case, since the modified region is formed from the second surface side opposite to the first surface, which is the incident surface of the laser beam, the modified region is not affected by the previously formed modified region. It is possible to form a modified region of

In the cutting method according to the present invention, in the first step, the modified region may be formed such that the width of the modified portion in the first direction is larger than the width of the cutting tool in the first direction. In this case, the influence of cleavage can be suppressed more reliably.

In the cutting method according to the present invention, in the first step, the modified region may be formed such that the modified region continuously extends from one end of the workpiece to the other end along the planned cutting line. . In this case, it is possible to cut the workpiece while reliably suppressing the influence of cleavage over the entire length of the workpiece.

A chip according to the present invention includes a gallium oxide substrate having a first surface, a second surface opposite to the first surface, and a side surface connecting the first surface and the second surface, and formed on the first surface. and a device layer, the side surface of which is constituted by a modified region.

According to the present invention, it is possible to provide a cutting method and chip capable of cutting a workpiece containing gallium oxide at high speed while suppressing the influence of cleavage.

FIG. 2 is a schematic configuration diagram of a laser processing device used to form a modified region. FIG. 3 is a plan view of a workpiece that is a target for forming a modified region. FIG. 3 is a cross-sectional view of the workpiece in FIG. 2 taken along line III-III. FIG. 3 is a plan view of the workpiece after laser processing. FIG. 5 is a cross-sectional view of the workpiece in FIG. 4 taken along line VV. FIG. 5 is a cross-sectional view of the workpiece in FIG. 4 taken along line VI-VI. It is a figure showing the workpiece cut by the cutting method concerning this embodiment. It is an enlarged perspective view for explaining the outline of the cutting method concerning this embodiment. FIG. 9 is a schematic cross-sectional view of the workpiece shown in FIG. 8(a). It is a figure showing a 1st process. It is a figure showing a 1st process. It is a figure showing the relationship between a modification part and a cutting tool. FIG. 2 is a perspective view showing a chip formed by the cutting method according to the present embodiment. It is a sectional view showing a modification of a modification part. It is a sectional view showing a modification of a modification part.

Hereinafter, an example of the method and apparatus according to the present embodiment will be described with reference to the drawings. In the explanation of the drawings, the same elements or corresponding elements may be given the same reference numerals, and redundant explanations may be omitted.

In the laser processing apparatus according to the embodiment, a modified region is formed in the workpiece along a line to be cut by focusing laser light on the workpiece. Therefore, first, the formation of the modified region will be explained with reference to FIGS. 1 to 6.

As shown in FIG. 1, the laser processing apparatus 100 includes a laser light source 101 that pulses laser light L, and a dichroic mirror 103 arranged to change the direction of the optical axis (optical path) of the laser light L by 90 degrees. , and a condensing lens 105 for condensing the laser beam L. The laser processing apparatus 100 also includes a support stand 107 for supporting the workpiece 1, which is an object to be irradiated with the laser beam L focused by the focusing lens 105, and a support stand 107 for moving the support stand 107. a stage 111 which is a movement mechanism of the stage 111, a laser light source control unit 102 which controls the laser light source 101 to adjust the output, pulse width, pulse waveform, etc. of the laser beam L, and a stage control unit 115 which controls the movement of the stage 111. It is equipped with.

In the laser processing apparatus 100, the direction of the optical axis of the laser beam L emitted from the laser light source 101 is changed by 90 degrees by the dichroic mirror 103, and the laser beam L is emitted from the inside of the workpiece 1 placed on the support table 107. The light is focused by a focusing lens 105. At the same time, 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 in the workpiece 1. Note that here, the stage 111 is moved in order to relatively move the laser beam L, but the condensing lens 105 may be moved, or both of these may be moved.

As the workpiece 1, a plate-shaped member (for example, a substrate, a wafer, etc.) including a semiconductor substrate made of a semiconductor material, a piezoelectric substrate made of a piezoelectric material, etc. is used. As shown in FIG. 2, a planned cutting line 5 for cutting the workpiece 1 is set on the workpiece 1. As shown in FIG. The planned cutting line 5 is an imaginary line extending linearly. When forming a modified region inside the workpiece 1, as shown in FIG. It is relatively moved along the planned line 5 (that is, in the direction of arrow A in FIG. 2). As a result, as shown in FIGS. 4, 5, and 6, a modified region 7 is formed in the workpiece 1 along the planned cutting line 5, and a modified region formed along the planned cutting line 5. 7 becomes the cutting starting point area 8. The scheduled cutting line 5 corresponds to the scheduled irradiation line.

The condensing point P is a location where the laser beam L is condensed. The planned cutting line 5 is not limited to a straight line, but may be curved, a three-dimensional combination of these lines, or a line with specified coordinates. The planned cutting line 5 is not limited to a virtual line, but may be a line actually drawn on the surface 3 of the workpiece 1. The modified region 7 may be formed continuously or intermittently. The modified regions 7 may be in the form of rows or dots, and the important thing is that the modified regions 7 should be formed at least inside the workpiece 1, on the front surface 3, or on the back surface. A crack may be formed starting from the modified region 7, and the crack and the modified region 7 may be exposed on the outer surface (the front surface 3, the back surface, or the outer peripheral surface) of the workpiece 1. The laser light incident surface when forming the modified region 7 is not limited to the front surface 3 of the workpiece 1, but may be the back surface of the workpiece 1.

Incidentally, when forming the modified region 7 inside the workpiece 1, the laser beam L is transmitted through the workpiece 1 and near the condensing point P located inside the workpiece 1. Especially absorbed. As a result, a modified region 7 is formed in the workpiece 1 (that is, internal absorption laser processing). In this case, the surface 3 of the workpiece 1 hardly absorbs the laser beam L, so the surface 3 of the workpiece 1 is not melted. On the other hand, when forming the modified region 7 on the front surface 3 or the back surface of the workpiece 1, the laser beam L is particularly absorbed near the condensing point P located on the front surface 3 or the back surface, and The material is melted and removed to form removed portions such as holes and grooves (surface absorption laser processing).

The modified region 7 is a region whose density, refractive index, mechanical strength, and other physical properties are different from those of the surrounding region. Examples of the modified region 7 include a melt-treated region (meaning at least one of a region once melted and then re-solidified, a region in a molten state, and a region in a state of re-solidification from melting), a crack region , dielectric breakdown region, refractive index change region, etc., and there are also regions in which these are mixed. Furthermore, the modified regions 7 include regions in which the density of the modified regions 7 has changed compared to the density of non-modified regions in the material of the workpiece 1, and regions in which lattice defects have been formed. When the material of the workpiece 1 is single crystal silicon, the modified region 7 can also be said to be a high dislocation density region.

The areas where the density of the melt-treated area, the refractive index change area, and the modified area 7 has changed compared to the density of the unmodified area, and the area where lattice defects are formed are further divided into the inside of these areas and the modified area. Cracks (cracks, microcracks) may be included at the interface between the region 7 and the unmodified region. The included cracks may extend over the entire surface of the modified region 7, may be formed only in one portion, or may be formed in multiple portions. The workpiece 1 includes a substrate made of a crystal material having a crystal structure. For example, the workpiece 1 is made of at least one of gallium oxide (Ga ₂ O ₃ ), gallium nitride (GaN), silicon (Si), silicon carbide (SiC), LiTaO ₃ , and sapphire (Al ₂ O ₃ ). including a formed substrate. In other words, the workpiece 1 includes, for example, a gallium nitride substrate, a silicon substrate, a SiC substrate, a LiTaO ₃ substrate, or a sapphire substrate. The crystal material may be either an anisotropic crystal or an isotropic crystal. Further, the workpiece 1 may include a substrate made of an amorphous material having an amorphous structure (amorphous structure), and may include a glass substrate, for example.

In the embodiment, the modified region 7 can be formed by forming a plurality of modified spots (processing marks) along the planned cutting line 5 . In this case, a plurality of modified spots come together to form a modified region 7. A 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. Regarding the modification spot, the size and length of cracks that occur are determined appropriately, taking into consideration the required cutting accuracy, required flatness of the cut surface, thickness, type, crystal orientation, etc. of the workpiece 1. can be controlled. Further, in the embodiment, a modified spot can be formed as a modified region 7 along the planned cutting line 5 .
[Cutting method according to embodiment]

Subsequently, a cutting method according to the embodiment will be described. FIG. 7 is a diagram showing a workpiece to be cut by the cutting method according to the present embodiment. FIG. 7(a) is a plan view, and FIG. 7(b) is a partial sectional view. The workpiece 1 shown in FIG. 7 includes gallium oxide (eg, Ga ₂ O ₃ ). More specifically, the workpiece 1 includes a substrate 11 containing gallium oxide and a device layer 12 formed on the substrate 11. The substrate 11 includes a first surface 11s (eg, surface 3 in FIG. 1) and a second surface 11r opposite to the first surface 11s.

The substrate 11 is, for example, a gallium oxide substrate (eg, a Ga ₂ O ₃ -based substrate). _A Ga _{2 O 3} - _based substrate is a β _- type ( _Al A substrate made of β-Ga ₂ O ₃ -based single crystal to be crystallized, and may contain impurities such as Cu, Ag, Zn, Cd, Al, In, Si, Ge, Sn, Mg, Nb, Fe, etc. . Ga ₂ O ₃ based substrates have strong cleavability in the (100) plane, and if the main surface (for example, the first surface 11s) is the (100) plane, peeling will occur, and if the main surface is in a plane other than the (100) plane, If it is a plane, cleavage is likely to occur. Therefore, the cutting method according to this embodiment is effective regardless of the orientation of the main surface of the Ga ₂ O ₃ -based substrate.

The device layer 12 is formed on the first surface 11s. The device layer 12 is a semiconductor operating layer formed, for example, by crystal growth, and includes a plurality of device parts 13 arranged two-dimensionally on the first surface 11s. The device section 13 is, for example, a light receiving element such as a photodiode, a light emitting element such as a laser diode, or a circuit element formed as a circuit. A street ST, which is a region where the first surface 11s is exposed, is provided between the device parts 13 adjacent to each other. The streets ST are arranged, for example, in a grid pattern. The scheduled cutting line 5 is set to the street ST. That is, the planned cutting line 5 is set in a two-dimensional grid shape so as to pass between the device parts 13 adjacent to each other.

FIG. 8 is an enlarged perspective view for explaining the outline of the cutting method according to this embodiment. FIG. 9 is a schematic cross-sectional view of the workpiece shown in FIG. 8(a). In FIGS. 8 and 9, only a portion of the workpiece 1 corresponding to the edges of the pair of device portions 13 and a portion corresponding to the street ST between the pair of device portions 13 are shown. Further, in the following drawings, the modified region 7 is shown by hatching, and the hatching of other parts may be omitted. Further, in the following drawings, a rectangular coordinate system defined by an X-axis, a Y-axis, and a Z-axis is shown for ease of understanding.

As shown in FIGS. 8 and 9, the cutting method according to the present embodiment includes a first step of forming a modified region 7 on the workpiece 1 along the scheduled cutting line 5, and a cutting step after the first step. A second step of cutting the workpiece 1 along the planned cutting line 5 by inserting a cutting tool 50 into the workpiece 1 along the planned cutting line 5 is included. In the first step, as will be described in detail later, by irradiating the workpiece 1 (substrate 11) with the laser beam L along the cutting line 5 while making the first surface 11s the incident surface of the laser beam L. , a modified region 7 is formed in the workpiece 1 along the planned cutting line 5 .

The laser beam L is an ultrashort pulse laser beam. More specifically, for example, the repetition frequency of the laser beam L is 200 kHz, the center wavelength of the laser beam L is 1030 nm, and the pulse width of the laser beam L is 10 ps or less (for example, several hundred fs or more and 10 ps or less).

In the first step, for one scheduled cutting line 5, the lines are arranged so as to intersect (orthogonal to) the scheduled cutting line 5 and in a first direction (here, the Y-axis direction) along the first surface 11s. By forming a plurality of rows (for example, 25 rows, 5 rows in the illustrated example) of modified regions 7 in , a modified portion 70 including a plurality of rows of modified regions 7 is formed. The modified region 7 extends in a third direction (here, the X-axis direction) that intersects (orthogonally) with the first direction and the second direction (here, the Z-axis direction) from the second surface 11r to the first surface 11s. They are formed in rows along the line. Further, in the first step, a plurality of rows (for example, nine rows, five rows in the illustrated example) of modified regions 7 are formed so as to be arranged in the second direction with respect to one scheduled cutting line 5. Thus, a modified portion 70 including a plurality of rows of modified regions 7 is formed. As a result, the modified portion 70 includes a plurality of modified regions 7 arranged in a matrix along the first direction and the second direction in a cross section that intersects (perpendicularly intersects) the planned cutting line 5. .

From one point of view, the modified region 70 is configured such that row-shaped modified regions 7 extending along the third direction are arranged along the second direction (that is, the modified regions 7 are arranged along the second direction and the third direction). It can be understood that the modified layer 7m (extending) is formed by laminating a plurality of modified layers 7m in the first direction. Moreover, from another viewpoint, the modified region 70 is configured such that row-shaped modified regions 7 extending along the third direction are arranged along the first direction (that is, the modified regions 7 extending in the first direction and the third direction are arranged in rows). It can also be considered that a plurality of modified layers 7n (extending along the direction) are laminated in the second direction. The modification portion 70 is formed here in a rectangular parallelepiped shape extending along the third direction. In addition, in FIG. 9 and the following figures, from the viewpoint of ease of illustration, the modified regions 7 that are adjacent to each other are illustrated as being separated from each other, but the modified regions 7 are partially or completely separated from each other. They may be formed continuously.

Subsequently, the first step will be explained in detail. 10 and 11 are diagrams showing the first step. In FIG. 10(b) and FIG. 11(b), the device section 13 is omitted. In the first step, as shown in FIG. 10(a), first, the first surface 11s is used as the incident surface of the laser beam L, and the convergence point P of the laser beam L is set on the workpiece 1 (substrate 11). or on the second surface 11r. Then, as shown in FIG. 10(b), by moving the condensing point P of the laser beam L relative to the workpiece 1, the laser beam L is irradiated onto the workpiece 1 (scanning). ). Thereby, as shown in FIG. 11, a modified region 7 is formed in the workpiece 1. Here, the modified region 7 is formed by scanning the workpiece 1 using the stage 111 while irradiating the laser beam L. The scan speed (speed of relative movement of the focal point P) is 500 mm/sec or less, more preferably 100 mm/sec or less.

In the first step, as shown in FIG. 10(b), while maintaining the position of the focal point P of the laser beam L in the second direction, the focal point P is moved along the first direction and the third direction. and move it relatively. Thereby, as shown in FIGS. 11(a) and 11(b), by forming a plurality of rows of modified regions 7 arranged along the first direction, a plurality of rows of modified regions 7 are included. A modified layer 7n is formed (modified layer forming step).

Subsequently, in the first step, the above modified layer forming step is repeated while changing the position of the condensing point P of the laser beam L in the second direction, thereby modifying the modified layer 7n so that the modified layer 7n is laminated. A region 7 is formed, and a modified portion 70 including a plurality of modified layers 7n is formed (see FIG. 9). In particular, in the first step, the modified layer forming step is repeated while sequentially changing the position of the focal point P of the laser beam L in the second direction from the second surface 11r side to the first surface 11s side. Thereby, the modified layers 7n are stacked sequentially from the second surface 11r side. Furthermore, in the first step, the modified region 7 is formed such that the modified portion 70 is exposed on both the first surface 11s and the second surface 11r. That is, here, the modified region 7 is formed so that the modified portion 70 extends continuously along the second direction to reach the first surface 11s and the second surface 11r. Furthermore, in the first step, the modified region 7 is formed such that the modified portion 70 continuously extends from one end of the workpiece 1 to the other end along the cutting line 5.

After the above first step, a second step is performed. In the second step, as described above, the workpiece 1 is cut along the cut line 5 by inserting the cutting tool 50 into the workpiece 1 along the cut line 5. The cutting tool 50 is, for example, a blade used for blade dicing, and includes a disc-shaped main body portion 51 and a blade portion 52 with a tapered cross section provided on the outer circumference of the main body portion 51. In the second step, such a cutting tool 50 is rotated about the center of the main body 51 as the rotation axis while bringing the blade 52 into contact with the workpiece 1 (substrate 11) along the planned cutting line 5. insert. Thereby, the workpiece 1 is cut along the planned cutting line 5 by cutting (removing) a part of the workpiece 1 .

Here, as shown in FIG. 12, in the first step, the modified region 7 is formed while defining the dimensions and shape of the modified portion 70 from the relationship with the cutting tool 50. Defining the dimensions and shape of the modified portion 70 in relation to the cutting tool 50 is based on the condition of the portion of the workpiece 1 to be cut (removed) by the cutting tool 50 (such as whether the entire portion is modified or not). ). In the present embodiment, in the first step, the modified region 7 form. Therefore, here, the entire portion of the workpiece 1 that is cut (removed) by the cutting tool 50 is a modified region.

As a result, chips are formed from the workpiece 1. FIG. 13 is a perspective view showing a chip formed by the cutting method according to this embodiment. As shown in FIG. 13, the chip C includes a substrate 11C formed from the substrate 11 and a device layer 12C (device section 13) formed from the device layer 12. The substrate 11C is, for example, a gallium oxide substrate. Further, like the substrate 11, the substrate 11C includes a first surface 11s and a second surface 11r opposite to the first surface 11s. Further, the substrate 11C includes a side surface 11p connecting the first surface 11s and the second surface 11r. Here, the surfaces other than the first surface 11s and the second surface 11r of the substantially rectangular parallelepiped substrate 11C are the side surfaces 11p.

As described above, the width W70 of the modified portion 70 is larger than the width W50 of the cutting tool 50, and the entire region of the workpiece 1 to be cut (removed) by the cutting tool 50 is the modified region 7 (modified region 70). The mass part 70). Therefore, the modified region 7 remains on the cut surface of the workpiece 1. In other words, the entire side surface 11p, which is a cut surface, is constituted by the modified region 7 (part 70C of the modified portion 70). Further, the side surface 11p is rougher than a cut surface or a cleavage surface obtained by cutting a crack extending from the modified region 7 that is caused to grow by external stress due to cutting marks of the cutting tool 50, for example.

The device layer 12C includes, for example, a homoepitaxial film or a heteroepitaxial film formed on the substrate 11 by epitaxial growth. Further, the device layer 12C may include, for example, an electrode formed on the surface opposite to the substrate 11C. Further, another electrode or the like may be formed on the second surface 11r of the substrate 11C. The chip C configured as described above is, for example, a semiconductor optical device such as an LED, or a semiconductor power device such as a diode or a transistor.

As explained above, in the cutting method according to the present embodiment, the workpiece 1 (substrate 11) to be cut contains gallium oxide. Therefore, when cutting the workpiece 1 only by blade dicing, it is necessary to reduce the cutting rate. Furthermore, when applying an external force to the workpiece 1 and performing cutting starting from the modified region 7, the influence of the cleavage plane of gallium oxide is likely to occur. On the other hand, in the cutting method according to the present embodiment, in the first step, the modified region 7 is formed along the planned cutting line 5, and in the second step, the modified region 7 is formed along the planned cutting line 5. The workpiece 1 is cut by inserting the cutting tool 50 into the object 1.

In this way, by performing cutting in a state that has become brittle due to the formation of the modified region 7 (for example, the crystallinity of gallium oxide has decreased), it is possible to cut the workpiece 1 while suppressing the influence of cleavage. becomes. In particular, in the first step, a modified portion 70 including a plurality of rows of modified regions 7 is formed for one scheduled cutting line 5 . Therefore, the modified portion 70 can be cut at high speed using the cutting tool 50 having a constant width W50. Therefore, according to the cutting method according to the present embodiment, the workpiece 1 containing gallium oxide can be cut at high speed while suppressing the influence of cleavage. Note that the speed of cutting (blade dicing) by the cutting tool 50 here can be, for example, 10 times or more of the conventional speed, or 2 mm/sec or more.

In the cutting method according to the present embodiment, in the first step, a plurality of rows are arranged in a second direction from the second surface 11r toward the first surface 11s with respect to one scheduled cutting line 5. The modified portion 70 may be formed by forming the modified region 7. In this case, since the modified portion 70 extends in the thickness direction (second direction) of the workpiece 1, it is possible to cut at a higher speed while reliably suppressing the influence of cleavage.

Further, in the cutting method according to the present embodiment, in the first step, a plurality of rows of modified regions 7 are formed while maintaining the position of the focal point P of the laser beam L in the second direction. By repeating the modified layer forming step of forming a modified layer 7n including a plurality of modified layers 7n while changing the position of the focal point P of the laser beam L in the second direction, a modified layer 7n including a plurality of modified layers 7n is formed. A mass part 70 is formed. In this way, if the modified part 70 is configured by laminating the modified layers 7n along the thickness direction (second direction) of the workpiece 1, the shape of the modified part 70 in the thickness direction can be changed. It becomes easier to control the state.

In particular, in the cutting method according to the present embodiment, in the first step, the position of the focal point P of the laser beam L in the second direction is sequentially changed from the second surface 11r side to the first surface 11s side. By repeating the layer forming process, a modified portion 70 including a plurality of modified layers 7n is formed. Therefore, since the modified region 7 is formed from the second surface 11r side opposite to the first surface 11s, which is the incident surface of the laser beam L, the influence of the previously formed modified region 7 It is possible to form the subsequent modified region 7 without receiving any damage.

Further, in the cutting method according to the present embodiment, in the first step, the modified region 7 is formed such that the width W70 of the modified portion 70 in the first direction is larger than the width W50 of the cutting tool 50 in the first direction. Form. Therefore, it is possible to secure a sufficient cutting allowance and suppress the influence of cleavage more reliably.

Furthermore, in the cutting method according to the present embodiment, in the first step, the modified region 70 extends continuously from one end of the workpiece 1 to the other end along the cutting line 5. form 7. Therefore, it is possible to cut the workpiece 1 over its entire length while reliably suppressing the influence of cleavage.

The above embodiment describes one embodiment of the cutting method according to the present invention. Therefore, the cutting method according to the present invention is not limited to the above-mentioned cutting method and can be modified as desired.

Further, as shown in FIGS. 14 and 15, the shape of the modified portion 70 in a cross section intersecting the planned cutting line 5 (a cross section along the first direction and the second direction) may be changed. In the example shown in FIG. 14A, the modified region 7 is formed so that the modified portion 70 has a tapered cross-sectional shape that decreases from the first surface 11s toward the second surface 11r. are doing. In the example of FIG. 14(b), the modified region 7 is formed so that the modified section 70 has a tapered cross-sectional shape that expands from the first surface 11s toward the second surface 11r. are doing.

In the example of FIG. 15(a), the modified area is arranged such that the cross-sectional shape of the modified portion 70 is such that it once shrinks and then expands as it goes from the first surface 11s to the second surface 11r. 7 is formed. In the example of FIG. 15(b), the modified region 7 is formed so that the cross-sectional shape of the modified portion 70 expands once and then contracts as it goes from the first surface 11s to the second surface 11r. is forming. Furthermore, in the example of FIG. 15(c), the modified region 7 is formed so that the cross-sectional shape of the modified portion 70 is wavy, which is bent multiple times from the first surface 11s toward the second surface 11r. There is. As in these examples, the cross-sectional shape of the modified portion 70 can be appropriately selected depending on, for example, the shape of the cutting tool 50 and the like. Note that the aspect (for example, shape) of the modified portion 70 in plan view can also be selected as appropriate depending on, for example, the shape of the cutting tool 50 and the like.

In addition, in the said embodiment, the example which formed the modified region 7 so that 7 n of modified layers extended along a 1st direction and a 3rd direction may be laminated|stacked from the 2nd surface 11r side was demonstrated. However, the modified region 7 may be formed by sequentially stacking the modified layers 7n from the first surface 11s side, or by stacking the modified layers 7m extending along the second and third directions in order. The modified region 7 may be formed in the. Furthermore, the modified regions 7 may be formed in a different order.

DESCRIPTION OF SYMBOLS 1... Workpiece, 5... Cutting line, 7... Modified area, 7n... Modified layer, 11C... Substrate, 11s... First surface, 11r... Second surface, 11p... Side surface, 12C... Device layer, 50 ...Cutting tool, 70... Modification part, C... Chip, L... Laser light, P... Focus point, W50, W70... Width.

Claims (6)

A cutting method that has a first surface and a second surface opposite to the first surface, and cuts a workpiece containing gallium oxide along a scheduled cutting line,
forming a modified region in the workpiece along the cutting line by irradiating the workpiece with a laser beam along the cutting line using the first surface as a laser beam incidence plane; 1 process and
After the first step, a second step of cutting the workpiece along the planned cutting line by inserting a cutting tool into the workpiece along the planned cutting line;
Equipped with
In the first step, for one scheduled cutting line, at least a plurality of rows of modified regions are arranged so as to intersect the scheduled cutting line and are arranged in a first direction along the first surface. forming a modified portion including a plurality of rows of the modified regions;
When a direction from the second surface to the first surface is defined as a second direction, and a direction intersecting the first direction and the second direction is defined as a third direction, in the first step, in the third direction, forming the modified portion by laminating a plurality of modified layers in the first direction, each of which has row-shaped modified regions arranged along the second direction;
Cutting method. A cutting method that has a first surface and a second surface opposite to the first surface, and cuts a workpiece containing gallium oxide along a scheduled cutting line,
forming a modified region in the workpiece along the cutting line by irradiating the workpiece with a laser beam along the cutting line using the first surface as a laser beam incidence plane; 1 process and
After the first step, a second step of cutting the workpiece along the planned cutting line by inserting a cutting tool into the workpiece along the planned cutting line;
Equipped with
In the first step, for one scheduled cutting line, at least a plurality of rows of modified regions are arranged so as to intersect the scheduled cutting line and are arranged in a first direction along the first surface. forming a modified portion including a plurality of rows of the modified regions;
When a direction from the second surface to the first surface is defined as a second direction, and a direction intersecting the first direction and the second direction is defined as a third direction, in the first step, in the third direction, forming the modified portion by stacking a plurality of modified layers in the second direction, each of which has row-shaped modified regions arranged along the first direction;
Cutting method. In the first step, the cross-sectional shape of the modified portion in a cross section intersecting the planned cutting line is tapered such that it decreases from the first surface toward the second surface, or from the first surface to the second surface. forming the modified portion so as to have a tapered shape that increases toward the second surface;
The cutting method according to claim 1 or 2. In the first step, the cross-sectional shape of the modified portion in a cross section intersecting the planned cutting line is such that the cross-sectional shape is once reduced and then expanded as it goes from the first surface to the second surface; The modified portion is formed so as to have a cross-sectional shape that expands once and then shrinks from the surface toward the second surface, or has a wavy shape that bends multiple times as it goes from the first surface toward the second surface. do,
The cutting method according to claim 1 or 2. In the first step, the modified region is formed such that the width of the modified portion in the first direction is larger than the width of the cutting tool in the first direction.
The cutting method according to any one of claims 1 to 4. In the first step, the modified region is formed so that the modified portion continuously extends from one end of the workpiece to the other end along the planned cutting line.
The cutting method according to any one of claims 1 to 5.

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