JP7186357B2 - Semiconductor device manufacturing method and semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device and a semiconductor device.

In general, semiconductor elements are obtained by dicing a wafer having a semiconductor layer formed on a substrate. As a method for dicing a wafer, a method is known in which a laser beam is focused inside a substrate to form a modified region, and the wafer is divided starting from cracks extending from the modified region. For example, Patent Document 1 describes a laser dicing method in which two rows of modified regions are formed in parallel in a dicing street by laser beam irradiation along a first straight line and a second straight line.

JP 2013-48207 A

In the method of Patent Literature 1, since cracks reaching the surface of the substrate are generated from each of the two rows of modified regions, there is a concern that chipping may occur in the substrate when the substrate is cut.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device and a semiconductor device that can suppress chipping of the substrate when the substrate is cut.

According to one aspect of the present invention, in a method for manufacturing a semiconductor device, a substrate having a first surface and a second surface is formed from the substrate along a first direction parallel to the first surface from the first surface side. By irradiating the inside of the substrate with a laser beam, a plurality of first modified portions arranged along the first direction and cracks extending from the first modified portions toward at least the first surface are formed inside the substrate. forming a first irradiation step, and after the first irradiation step, the first surface is shifted from the first modified portion in a second direction that intersects the first direction and is parallel to the first surface. a second irradiation step of irradiating a laser beam from the side to form a plurality of second modified portions arranged along the first direction at positions adjacent to the plurality of first modified portions in the second direction; , after the second irradiation step, a laser beam is irradiated along the first direction from the first surface side to reduce the thickness of the substrate on the first surface side of the first modified portion. a third irradiation step of forming a plurality of third modified portions arranged along the first direction at positions overlapping the plurality of first modified portions in plan view in the vertical direction ; and after the third irradiation step, pressing the substrate from the second surface side with a pressing member to cut the substrate. A modified portion is not formed at a position adjacent to the third modified portion in the second direction and overlapping the second modified portion in a plan view in the thickness direction of the substrate.

According to the method for manufacturing a semiconductor device and the semiconductor device of the present invention, chipping of the substrate can be suppressed when the substrate is cut.

1 is a schematic plan view of a wafer according to an embodiment of the invention; FIG. 1 is a schematic cross-sectional view of a wafer according to an embodiment of the invention; FIG. FIG. 4 is a schematic cross-sectional view showing a first irradiation step in the method for manufacturing a semiconductor device according to the first embodiment of the present invention; It is a schematic plan view which shows the 1st irradiation process in the manufacturing method of the semiconductor device of 1st Embodiment of this invention. It is a schematic cross section showing a second irradiation step in the method for manufacturing a semiconductor device according to the first embodiment of the present invention. It is a schematic plan view which shows the 2nd irradiation process in the manufacturing method of the semiconductor device of 1st Embodiment of this invention. It is a schematic cross-sectional view showing a third irradiation step in the method for manufacturing a semiconductor device according to the first embodiment of the present invention. It is a schematic plan view which shows the 3rd irradiation process in the manufacturing method of the semiconductor device of 1st Embodiment of this invention. FIG. 4 is a schematic cross-sectional view showing a cutting step in the method for manufacturing a semiconductor device according to the embodiment of the present invention; It is a schematic plan view which shows the cutting process in the manufacturing method of the semiconductor element of embodiment of this invention. It is a schematic plan view which shows the cutting process in the manufacturing method of the semiconductor element of embodiment of this invention. FIG. 10 is a schematic cross-sectional view showing a laser light irradiation step in the method for manufacturing a semiconductor device according to the second embodiment of the present invention; FIG. 10 is a schematic cross-sectional view showing a laser light irradiation step in the method for manufacturing a semiconductor device according to the third embodiment of the present invention; FIG. 11 is a schematic cross-sectional view showing a laser light irradiation step in a method for manufacturing a semiconductor device according to a fourth embodiment of the present invention; 1 is a schematic cross-sectional view of a semiconductor device manufactured according to one embodiment of the present invention; FIG.

Hereinafter, embodiments will be described with reference to the drawings. In addition, the same code|symbol is attached|subjected to the same structure in each drawing.

A method of manufacturing a semiconductor device according to an embodiment of the present invention includes a step of preparing a wafer, a step of irradiating a laser beam, and a step of cutting the wafer.

FIG. 1 is a schematic plan view of the wafer W of the embodiment. FIG. 2 is a schematic cross-sectional view of a portion of the wafer W on which the dicing streets D are formed.

A wafer W has a substrate 10 and a semiconductor layer 20 . The substrate 10 has a first side 11 and a second side 12 opposite the first side 11 . A semiconductor layer 20 is provided on the second surface 12 of the substrate 10 .

Substrate 10 is, for example, a sapphire substrate. The first surface 11 is, for example, the c-plane of sapphire. The first surface 11 may be inclined with respect to the c-plane as long as the semiconductor layer 20 can be formed with good crystallinity. In FIG. 1 , the X direction and the Y direction represent two directions orthogonal to each other within a plane parallel to the first surface 11 of the substrate 10 . For example, the X direction is along the m-axis direction of sapphire and the Y direction is along the a-axis direction of sapphire.

The semiconductor layer 20 includes, for example, a nitride semiconductor represented by In _x Al _y Ga _1-x-y N (0≦x, 0≦y, x+y<1). Semiconductor layer 20 includes an active layer. The active layer is, for example, an active layer that emits light. The peak wavelength of light emitted by the active layer is, for example, 280 nm or more and 650 nm or less. The peak wavelength of light emitted from the active layer may be 280 nm or less or 650 nm or more.

A plurality of dicing streets D are formed on the wafer W, for example, in a grid pattern. A dicing street D is a boundary area between a plurality of semiconductor elements separated into individual pieces by cutting the wafer W, and is an area set with a margin (width) that does not affect the semiconductor elements by cutting the wafer W. be. The dicing street D is also a laser beam scanning area for forming a modified portion, which will be described later, in the substrate 10 .

For example, the semiconductor layer 20 is not formed on the dicing street D. FIG. Dicing streets D separate the plurality of semiconductor layers 20 on the second surface 12 of the substrate 10 . The semiconductor layer 20 may be formed on the entire second surface 12 of the substrate 10 without being separated by the dicing streets D. FIG.

The method of manufacturing a semiconductor device according to the embodiment includes a step of irradiating a laser beam after the step of preparing the wafer W. FIG.

The laser light is scanned along each of the plurality of dicing streets D while irradiating the inside of the substrate 10 from the first surface 11 side. A laser beam is first scanned along a dicing street D extending in one of the X and Y directions shown in FIG. 1, and then scanned along a dicing street D extending in the other direction. .

The laser light is emitted, for example, in a pulse shape. The pulse width of the laser light is 100 fsec to 1000 psec. As a laser light source, for example, an Nd:YAG laser, a titanium sapphire laser, an Nd: _YVO4 laser, or an Nd:YLF laser is used. The wavelength of the laser light is the wavelength of light that passes through the substrate 10 . Laser light has a peak wavelength in the range of 500 nm or more and 1200 nm or less, for example.

The laser beam irradiation step includes a first irradiation step, a second irradiation step, and a third irradiation step.

[First embodiment]
<First irradiation step>
FIG. 3A is a schematic cross-sectional view showing the first irradiation step in the first embodiment.
FIG. 3B is a schematic plan view showing the first irradiation step in the first embodiment.

In FIGS. 3A and 3B, the scanning direction of the laser light is assumed to be the first direction d1. The first direction d1 is a direction parallel to the first surface 11 of the substrate 10 . When the laser beam is scanned along the X direction shown in FIG. 1, the first direction d1 is parallel to the X direction, and when the laser beam is scanned along the Y direction shown in FIG. parallel to the Y direction. A direction crossing the first direction d1 is defined as a second direction d2. For example, the second direction d2 is orthogonal to the first direction d1.

In the first irradiation step of the first embodiment, the inside of the substrate 10 is irradiated with laser light from the first surface 11 side of the substrate 10 along the first direction d1. The laser light is condensed at a predetermined depth inside the substrate 10, and the energy of the laser light is concentrated at that position. A modified portion that is more embrittled than the portion not irradiated with the laser beam is formed in the portion irradiated with the laser beam (condensing portion). Further, for example, the modified portion is a portion having a lower light transmittance than the portion not irradiated with the laser beam. Here, the position set when irradiating the laser light from the first surface 11 side in the substrate 10 and the position where the modified portion is actually formed may deviate. In that case, the position to be irradiated with the laser light can be adjusted in consideration of the amount of deviation. The first modified portion a is formed by this first irradiation step. Further, strain is generated in the first modified portion a, and crack cr is generated from the first modified portion a by releasing the strain. A crack cr extending from the first modified portion a through the inside of the substrate 10 toward at least the first surface 11 is formed. The laser light output (pulse energy) for forming the first modified portion a is, for example, preferably 0.1 μJ or more and 20.0 μJ or less, more preferably 1.0 μJ or more and 15.0 μJ or less, and 2.0 μJ or more. 10.0 μJ or less is more preferable.

A laser beam is discretely scanned along the first direction d1 within the range of the dicing street D, and as shown in FIG. a is formed. The plurality of first modified portions a are, for example, discretely formed along the first direction d1. Alternatively, a plurality of first modified portions a may be formed in a continuous line shape extending in the first direction d1 by partially contacting (or overlapping) the first modified portions a adjacent in the first direction d1. good.

<Second irradiation step>
FIG. 4A is a schematic cross-sectional view showing a second irradiation step in the first embodiment.
FIG. 4B is a schematic plan view showing a second irradiation step in the first embodiment;

After the first irradiation step, a second irradiation step is performed. In the second irradiation step, a laser beam is irradiated from the first surface 11 side to a position shifted in the second direction d2 from the first modified portion a. A second modified portion b is formed inside the substrate 10 by this second irradiation step.

The irradiation position of the laser beam in the thickness direction of the substrate 10 when forming the second modified portion b is almost the same as the irradiation position of the laser beam in the thickness direction of the substrate 10 when forming the first modified portion a. in the same position. Therefore, the position of the second modified portion b in the thickness direction of the substrate 10 is substantially the same as the position of the first modified portion a in the thickness direction of the substrate 10 . The term “substantially the same” as used herein means that a deviation of 10 μm or less is permissible, and a deviation of 5 μm or less is preferable. The first modified portion a and the second modified portion b are adjacent to each other within the range of the dicing street D in the second direction d2. Here, “the first modified portion a and the second modified portion b are adjacent to each other in the second direction d2 within the range of the dicing street D” means that the first modified portion a and the second modified portion It is sufficient that at least part of the material b is adjacent to each other in the second direction d2. For example, the first modified section a and the second modified section b are separated in the second direction d2. Alternatively, a portion of the first modified portion a and a portion of the second modified portion b may contact or overlap in the second direction d2. When a portion of the first modified portion a and a portion of the second modified portion b overlap, a portion of the first modified portion a and a portion of the second modified portion in the region where the modified portion is formed The strength of the region where a part of b is overlapped is the region where a part of the first modified part a and a part of the second modified part b do not overlap in the region where the modified part is formed. can be higher than the intensity of Therefore, when the first modified portion a and the second modified portion b are separated in the second direction d2, the modified portions do not overlap each other inside the substrate 10 and the modified portions are not densely formed. In the step of breaking the wafer W, which will be described later, the force required to break the wafer W can be reduced. When the first modified portion a and the second modified portion b are separated in the second direction d2, the shortest distance between the first modified portion a and the second modified portion b is preferably 0.1 μm or more and 2 μm or less.

A laser beam is discretely scanned along the first direction d1 at positions shifted in the second direction d2 from the first modified portion a. As shown in FIG. 4B, a plurality of modified regions b arranged along the first direction d1 are formed at positions adjacent to the plurality of first modified regions a arranged along the first direction d1 in the second direction d2. be done.

When a plurality of first modified portions a are discretely formed along the first direction d1, a plurality of second modified portions a are aligned with the positions of the respective first modified portions a in the first direction d1. b may also be discretely formed along the first direction d1. Alternatively, when portions of the first modified portions a adjacent in the first direction d1 contact (or overlap) to form a plurality of first modified portions a in a continuous line extending in the first direction d1. , the plurality of second modified portions b may also be formed in a continuous line shape extending in the first direction d1, with portions thereof adjacent to each other in the first direction d1 contacting (or overlapping). Either one of the plurality of first modified portions a and the plurality of second modified portions b may be formed in a continuous line shape extending in the first direction d1.

By forming the second modified portion b next to the first modified portion a in the second direction d2, the extension of the crack cr generated from the first modified portion a can be promoted. Cracks arise from the modified portion due to the release of the strain that occurs during the formation of the modified portion. In addition, when a new modified portion is formed in the vicinity of the region where the modified portion is formed and cracks have already occurred, the force generated when the strain is released is newly generated from the newly formed modified portion. It is presumed that it works not only for cracks but also for cracks that have already occurred. In other words, the force when the strain generated when forming the second modified portion b is released acts on the crack extending from the already formed first modified portion a, so that the first modified portion b It is presumed that the extension of the crack extending from the portion a toward the first surface 11 of the substrate 10 is promoted. The laser beam output for forming the second modified portion b is, for example, preferably 0.1 μJ or more and 20.0 μJ or less, more preferably 1.0 μJ or more and 15.0 μJ or less, and 2.0 μJ or more and 10.0 μJ or less. is more preferred.

<Third irradiation step>
FIG. 5A is a schematic cross-sectional view showing a third irradiation step in the first embodiment;
FIG. 5B is a schematic plan view showing a third irradiation step in the first embodiment;

After the second irradiation step, a third irradiation step is performed. In the third irradiation step, laser light is irradiated from the first surface 11 side of the substrate 10 along the first direction d1. A third modified portion c is formed inside the substrate 10 by this third irradiation step. The irradiation position of the laser beam in the thickness direction of the substrate 10 when forming the third modified portion c is higher than the irradiation position of the laser beam in the thickness direction of the substrate 10 when forming the first modified portion a. close to the first surface 11; Therefore, the position of the third modified portion c in the thickness direction of the substrate 10 is closer to the first surface 11 than the position of the first modified portion a in the thickness direction of the substrate 10 . Furthermore, the third modified portion c is formed at a position overlapping the first modified portion a in a plan view in the thickness direction of the substrate 10 . The first modified portion a and the third modified portion c are separated in the thickness direction of the substrate 10 .

In the third irradiation step, the laser light is discretely scanned along the first direction d1, and the thickness of the substrate 10 is closer to the first surface 11 than the first modified portion a inside the substrate 10. A plurality of third modified portions c arranged along the first direction d1 are formed at positions overlapping the plurality of first modified portions a in plan view in the direction.

When the plurality of first modified portions a are discretely formed along the first direction d1, the plurality of third modified portions c may also be discretely formed along the first direction d1. Alternatively, when portions of the first modified portions a adjacent in the first direction d1 contact (or overlap) to form a plurality of first modified portions a in a continuous line extending in the first direction d1. , the plurality of third modified portions c may also be formed in a continuous line shape extending in the first direction d1, with portions thereof adjacent to each other in the first direction d1 contacting (or overlapping). Further, one of the plurality of first modified portions a and the plurality of third modified portions c may be formed in a continuous line shape extending in the first direction d1.

Strain is generated by forming the third modified portion c, and crack cr is generated from the third modified portion c by releasing the strain. The third modified portion c is located at a position overlapping the first modified portion a in plan view in the thickness direction of the substrate 10 . Therefore, when there is a crack cr extending from the third modified portion c toward the second surface 12, the crack cr is connected to the crack cr extending from the first modified portion a toward the first surface 11. can be done.

A crack cr extending from the third modified portion c toward the first surface 11 reaches the first surface 11 . Alternatively, the crack cr extending from the third modified portion c toward the first surface 11 reaches a position close to the first surface 11 . In any case, the crack cr extending from the third modified portion c toward the first surface 11 is positioned farther from the first surface 11 (closer to the second surface 12) than the third modified portion c. It reaches a position closer to the first surface 11 than the crack cr extending from a certain second modified portion b toward the first surface 11 . Cracks extending from the second modified portion b do not reach the first surface 11 or hardly reach the first surface 11 .

The first irradiation process, the second irradiation process, and the third irradiation process described above are performed for each of the plurality of dicing streets D shown in FIG.

<Creating process of wafer W>
After the third irradiation step, a step of cutting the wafer W is performed.
6A and 6B are schematic cross-sectional views showing the cutting process of the wafer W. FIG.

The surface of the wafer W on which the semiconductor layer 20 is formed is adhered to the sheet 30 . Then, the pressing member 40 presses the substrate 10 from the second surface 12 side through the sheet 30 . The pressing member 40 is, for example, a blade-shaped member extending along the dicing street D, and the substrate 10 that receives the pressing force of the pressing member 40 from the second surface 12 side extends from the third modified portion c. Cracks that reach or near the first surface 11 begin to crack. That is, a groove 15 having a V-shaped cross section that opens to the first surface 11 is formed along the dicing street D, and this groove 15 reaches the second surface 12, and the wafer W is cut. Any other method may be used as long as the cracking of the wafer W starts from a crack that extends from the third modified portion c and reaches the first surface 11 or near the first surface 11. good.

For example, first, the wafer W is cleaved along the dicing streets D extending along the X direction, and as shown in FIG. 7A, the wafer W is separated into a plurality of bars 50 extending along the X direction.

Thereafter, the bar 50 is cut along the dicing streets D extending along the Y direction, and the wafer W is singulated into a plurality of semiconductor devices 1 as shown in FIG. 7B. Alternatively, the cutting along the Y direction may be performed first, and then the cutting along the X direction may be performed.

On the side surface of each individual semiconductor element 1 that has been singulated, the above-described modified portions a and c are exposed as regions having a larger surface roughness than portions where the modified portions are not formed.

According to the first embodiment described above, by forming the second modified portion b next to the first modified portion a, the crack generated from the first modified portion a is directed toward the first surface 11. Stretching can be promoted. As a result, even the thick substrate 10 can be easily broken. The thickness of the substrate 10 is, for example, 100 μm or more and 1500 μm or less, preferably 150 μm or more and 1200 μm or less, and more preferably 300 μm or more and 1000 μm or less.

The distance between the centers of the first modified portion a and the second modified portion b in the second direction d2 within the range of one dicing street D is the strain generated when forming the second modified portion b. The force when released acts on the crack extending from the already formed first modified portion a, and extends the crack extending from the first modified portion a toward the first surface 11 of the substrate 10. It is set within the possible range. For example, the distance between the centers of the first modified portion a and the second modified portion b in the second direction d2 is preferably 2 μm or more and 10 μm or less.

A modified portion is not formed at a position adjacent to the third modified portion c in the second direction d2 and overlapping the second modified portion b in a plan view in the thickness direction of the substrate 10 . Within the range of one dicing street D, there is no modified portion adjacent to the third modified portion c in the second direction d2. In a position adjacent to the third modified portion c in the second direction d2 and overlapping within the range from the first modified portion a to the second modified portion b in plan view in the thickness direction of the substrate 10, a modified There is no quality department.

Therefore, at a position next to the crack reaching or near the first surface 11 in the second direction d2 from the third modified portion c, there is a Close reaching cracks are less likely to form. A crack from the second modified portion b does not reach closer to the first surface 11 than a crack from the third modified portion c. Within the range of one dicing street D, cracks reaching the first surface 11 or reaching near the first surface 11 are limited to cracks extending from the third modified portion c, and cracks from the first surface 11 side The number of cracks contributing to initiation can be reduced. For example, it is possible to limit the crack that contributes to crack initiation from the first surface 11 side to one crack that extends from the third modified portion c. As a result, cracks extending toward the first surface 11 are easily formed, while chipping of the substrate 10 when the substrate 10 starts to crack from the first surface 11 side is suppressed.

After the third irradiation step, a fourth irradiation step of irradiating a laser beam from the first surface 11 side under the condition that the modified portion can be formed can be provided. The fourth irradiation step is a step of irradiating the same position as the third modified portion c with a laser beam. This fourth irradiation step accelerates the extension of cracks extending from the third modified portion c toward the first surface 11 , making it easier for the cracks to reach the first surface 11 . When the crack reaches the first surface 11, the substrate 10 tends to crack from the first surface 11 side. Even in this case, since no modified portion is formed next to the third modified portion c in the second direction d2, the crack reaching the first surface 11 within the range of one dicing street D is the third modified portion Cracks extending from c can be restricted, and chipping of the substrate 10 can be suppressed. The conditions under which the modified portion can be formed are, for example, the same conditions as in the third irradiation step. At the same position as the third modified portion c, part or all may not be further modified by the fourth irradiation step, and part or all may be further modified. . Moreover, in addition to the third modified portion c, a new modified portion may be formed.

Since the semiconductor layer 20 is provided on the second surface 12 of the substrate 10, the irradiation position of the laser beam in the first irradiation step is the second surface 12 in order to suppress the thermal damage of the semiconductor layer 20 due to the irradiation of the laser beam. , is preferably a predetermined distance (a distance at which the semiconductor layer 20 is not thermally damaged) or more.

In addition, when the pressing member 40 applies a pressing force from the second surface 12 side, cracking starts from the first surface 11 side. Cracks from the core easily reach the first surface 11 and are easily broken.

Therefore, as shown in FIG. 5A, the first modified portion a is arranged so that the distance s1 from the first modified portion a to the second surface 12 is greater than the distance s2 from the third modified portion c to the first surface 11. It is preferable to form the modified portion a and the third modified portion c. When the thickness of the substrate 10 is 300 μm or more and 1000 μm or less, the distance s1 is, for example, 100 μm or more and 300 μm or less, and the distance s2 is, for example, 50 μm or more and 200 μm or less. However, even when the thickness of the substrate 10 is 300 μm or less, the distance s1 from the first modified portion a to the second surface 12 is longer than the distance s2 from the third modified portion c to the first surface 11. Thus, it is preferable to form the first modified portion a and the third modified portion c.

[Second embodiment]
FIG. 8 is a schematic cross-sectional view showing a laser beam irradiation step in the method for manufacturing a semiconductor device according to the second embodiment of the present invention.

In the present embodiment, before the third irradiation step, the first irradiation step and the second irradiation step are repeated to form a pair of the first modified portion and the second modified portion adjacent in the second direction d2. A plurality of pairs are formed in the thickness direction of the substrate 10 .

A first pair of a first modified portion a1 and a second modified portion b1 adjacent in the second direction d2 is formed at a position closest to the second surface 12 . A second pair of the first modified portion a2 and the second modified portion b2 adjacent in the second direction d2 is formed at a position closer to the first surface 11 than the first pair. A third pair of the first modified portion a3 and the second modified portion b3 adjacent in the second direction d2 is formed at a position closer to the first surface 11 than the second pair. A fourth pair of the first modified portion a4 and the second modified portion b4 adjacent in the second direction d2 is formed at a position closer to the first surface 11 than the third pair. Each pair is arranged along the first direction d1, like the first modified section a and the second modified section b in the first embodiment.

The third modified portion c is formed at a position closer to the first surface 11 than the fourth pair of first modified portions a4. The third modified portion c and the first modified portions a1 to a4 overlap in plan view in the thickness direction of the substrate 10, and the center of the third modified portion c and the centers of the first modified portions a1 to a4 are They are located on the same line (virtually represented by a one-dot chain line in FIG. 8) in the thickness direction of the substrate 10 .

The second modified portions b1 to b4 overlap when viewed from above in the thickness direction of the substrate 10, and the centers of the second modified portions b1 to b4 are on the same line (virtually represented by a dashed line in FIG. 8). To position.

The first irradiation step and the second irradiation step to the same depth are successively performed, and the deeper modified portion is formed earlier. That is, the first irradiation step and the second irradiation step are alternately repeated, and the first modified portion a1, the second modified portion b1, the first modified portion a2, the second modified portion b2, the first modified portion A3, a second modified portion b3, a first modified portion a4, and a second modified portion b4 are formed in this order. After that, a third modified portion c is formed by a third irradiation step.

In the second embodiment as well, the modified portions are adjacent to the third modified portion c in the second direction d2 and overlap the second modified portions b1 to b4 in plan view in the thickness direction of the substrate 10. do not form a part.

According to the second embodiment, by forming a plurality of pairs of the first modified portions a1 to a4 and the second modified portions b1 to b4 in the thickness direction of the substrate 10, even the thick substrate 10 can be It is easy to extend cracks in the thickness direction, and it is possible to break easily. In addition, by not forming a modified portion at a position adjacent to the third modified portion c in the second direction d2 and overlapping the second modified portions b1 to b4 in plan view in the thickness direction of the substrate 10, , chipping of the substrate 10 when the substrate 10 starts to crack from the first surface 11 side is suppressed.

When the output of the laser beam irradiated into the inside of the substrate 10 from the first surface 11 side is constant in the thickness direction of the substrate 10 , the laser beam is concentrated due to absorption in the substrate 10 at positions farther from the first surface 11 . The energy of the light part tends to be low. As a result, in a plurality of pairs of the first modified portions a1 to a4 and the second modified portions b1 to b4, the size of the modified portion tends to be smaller for pairs farther from the first surface 11 (closer to the second surface 12). . Therefore, as shown in FIG. 8, the distance between the first modified portions a1 to a4 and the second modified portions b1 to b4 in the second direction d2 increases as the pair is farther from the first surface 11 . That is, the farther the pair is from the first surface 11, the weaker the influence of the second modified portions b1 to b4 on the promotion of crack extension of the adjacent first modified portions a1 to a4. In the second embodiment, the shortest distance in the second direction d2 between the pair of the first modified portion and the second modified portion closest to the third modified portion c is preferably 0.1 μm or more and 2 μm or less. Moreover, the shortest distance in the second direction d2 between the pair of the first modified portion and the second modified portion that is the farthest from the first surface 11 is preferably 0.1 μm or more and 6 μm or less. By setting the range of the distance in the second direction d2 between the pair of the first modified portion and the second modified portion that are the farthest from the first surface 11, the second modified portion is placed in the adjacent first modified portion. It is possible to easily affect the promotion of crack extension in the modified portion.

[Third embodiment]
FIG. 9 is a schematic cross-sectional view showing a laser beam irradiation step in the method for manufacturing a semiconductor device according to the third embodiment of the present invention. In FIG. 9, a line passing through the center of each modified portion in the second direction d2 and extending along the thickness direction of the substrate 10 is virtually represented by a one-dot chain line.

The third embodiment differs from the second embodiment shown in FIG. 8 in the following points. That is, in the third embodiment, in a plurality of pairs of the first modified portions a1 to a4 and the second modified portions b1 to b4, the closer the pair is to the second surface 12, the center of the first modified portions a1 to a4. , the distance in the second direction d2 from the centers of the second modified portions b1 to b4 is small.

In the third embodiment, in the second irradiation step for forming the second modified portions b1 to b4, the position farther from the first surface 11 where the size of the second modified portions b1 to b4 tends to be smaller is irradiated with the laser beam. The position (light condensing position) is brought closer to the first modified portions a1 to a4. The output of the laser light irradiated into the inside of the substrate 10 from the first surface 11 side is constant in the thickness direction of the substrate 10 . As a result, variations in the separation distance in the second direction d2 between the first modified portions a1 to a4 and the second modified portions b1 to b4 depending on the position in the thickness direction of the substrate 10 are reduced, and the first modified portions a1 to a4 and the second modified portions b1 to b4 are separated from each other in the second direction d2. In the second reformed section, it is possible to suppress the weakening of the influence of the adjacent first reformed section on the promotion of crack extension.

[Fourth Embodiment]
FIG. 10 is a schematic cross-sectional view showing a laser beam irradiation step in the method for manufacturing a semiconductor device according to the fourth embodiment of the present invention. In FIG. 10, a line passing through the center of each modified portion in the second direction d2 and extending along the thickness direction of the substrate 10 is imaginarily represented by a one-dot chain line.

In the fourth embodiment, among a plurality of pairs of the first modified portions a1 to a4 and the second modified portions b1 to b4, the closer the pair is to the second surface 12, the higher the output of the laser beam is. This embodiment is the same as the second embodiment except that the second modified portions b1 to b4 are formed.

The farther away from the first surface 11, the lower the energy of the laser beam condensing portion tends to be. The energy that promotes crack extension in the 1 modified portions a1 to a4 tends to be insufficient. Therefore, in the fourth embodiment, the output of the laser beam is increased at positions farther from the first surface 11 to form the first modified portions a1 to a4 and the second modified portions b1 to b4. As a result, insufficient extension of cracks at positions far from the first surface 11 can be suppressed.

In the second to fourth embodiments shown in FIGS. 8 to 10, for example, the substrate 10 has a thickness of 700 μm, and the first modified portion a1 and the second modified portion b1 are separated from the first surface 11 by a distance of 550 μm, the first modified portion a2 and the second modified portion b2 are formed at a distance of 420 μm from the first surface 11, and the first modified portion a3 and the second modified portion b3 are formed. The distance from the first surface 11 is formed at a position of 300 μm, the first modified portion a4 and the second modified portion b4 are formed at a position at a distance of 210 μm from the first surface 11, and the third modified portion c is formed at a position at a distance of 120 μm from the first surface 11 . Here, the position set when irradiating the laser beam from the first surface 11 side in the substrate 10 and the position where the modified portion is actually formed may deviate. In that case, the position to be irradiated with the laser light can be adjusted in consideration of the amount of deviation.

In the second and third embodiments, the laser beam output for forming the first modified portions a1 to a4, the second modified portions b1 to b4, and the third modified portion c is, for example, 6 .0 μJ.

In the fourth embodiment, for example, the output of the laser beam for forming the third modified portion c is 6.0 μJ, and the laser beam for forming the first modified portion a4 and the second modified portion b4 is is 7.0 μJ, the output of the laser beam for forming the first modified portion a3 and the second modified portion b3 is 8.0 μJ, and the first modified portion a2 and the second modified portion The laser beam output for forming b2 is 9.0 μJ, and the laser beam output for forming the first modified portion a1 and the second modified portion b1 is 10.0 μJ.

In the second embodiment and the fourth embodiment, the center-to-center distance in the second direction d2 between the first reformed section a1 and the second reformed section b1, the distance between the first reformed section a2 and the second reformed section b2 The distance between the centers in the second direction d2, the distance between the centers in the second direction d2 between the first modified portion a3 and the second modified portion b3, and the distance between the first modified portion a4 and the second modified portion b4 The center-to-center distance in the two directions d2 is, for example, 6.0 μm.

In the third embodiment, for example, the center-to-center distance in the second direction d2 between the first modified portion a1 and the second modified portion b1 is 4.0 μm, and the first modified portion a2 and the second modified portion The center-to-center distance in the second direction d2 is 4.5 μm, the center-to-center distance in the second direction d2 between the first modified portion a3 and the second modified portion b3 is 5.0 μm, and the first The center-to-center distance in the second direction d2 between the modified portion a4 and the second modified portion b4 is 5.5 μm.

In the second to fourth embodiments shown in FIGS. 8 to 10 as well, after the third irradiation step, a fourth irradiation step of irradiating a laser beam from the first surface 11 side onto a position overlapping the third modified portion c. can also be provided.

Further, in the second to fourth embodiments, the distance from the first modified portion a1 closest to the second surface 12 among the first modified portions a1 to a4 to the second surface 12 is the third modified portion By forming the first modified portions a1 to a4 and the third modified portion c so as to be larger than the distance from c to the first surface 11, thermal damage to the semiconductor layer 20 due to laser light irradiation is suppressed. This makes it easier for cracks to reach the first surface 11 from the third modified portion c, thereby facilitating breaking.

In the second to fourth embodiments, four pairs of the first modified portions a1 to a4 and the second modified portions b1 to b4 are shown. They may be superimposed in plan view in the thickness direction.

In addition, in the first to fourth embodiments, it is preferable that no other modified portion is formed between the third modified portion c and the first surface 11 . Further, it is preferable that no other reformed section is formed between the third reformed section c and the first reformed section a and the second reformed section b.

Referring to FIG. 11, a cross-sectional view of a semiconductor device 1 manufactured according to one embodiment of the present invention is shown. The semiconductor element 1 shown in FIG. A first electrode 51 and a second electrode 52 are shown formed. Also, the semiconductor layer 20 includes a first semiconductor layer 201, an active layer 202, and a third semiconductor layer 203 in this order from the second surface 12 side. The active layer 202 is, in other words, the second semiconductor layer 202 . The first semiconductor layer 201 is, for example, n-type, and the third semiconductor layer 203 is, for example, p-type. The first electrode 51 is formed to connect to the first semiconductor layer 201 and the second electrode 52 is formed to connect to the third semiconductor layer 203 . The side surface of the substrate 10 has a first region where the modified portion a is exposed and a second region where the modified portion c is exposed. For example, in the substrate 10, the modified portion is a portion having a lower light transmittance than the portion where the modified portion is not formed. The first region extends along the first direction parallel to the first surface 11 (the direction penetrating through the paper in FIG. 11) at a position away from the first surface 11 and the second surface 12 . The second region extends along the first direction at a position between the first region and the first surface 11 and away from the first surface 11 . A portion of the side surface of the substrate 10 where the first region and the second region are not formed is a flat region with a relatively small surface roughness, and the surface roughness of the first region and the second region is the surface of the flat region. greater than roughness. The surface roughness of the side surface of the substrate 10 can be measured using, for example, a laser microscope. For example, the surface roughness Rz of the first region and the second region is 3 μm or more and 7 μm or less. For example, the flat region has a surface roughness Rz of 0.1 μm or more and 2.5 μm or less. In addition, a modified portion b is formed inside the substrate 10 adjacent to the modified portion a on one side surface of the substrate 10, and the plurality of modified portions b are formed inside the substrate 10 in the first region. , are aligned along the first direction at positions shifted in the second direction that intersect the first direction and are parallel to the first surface 11 . The modified portion b is not formed in the substrate 10 next to the modified portion a on the other side surface of the substrate 10 .

The embodiments of the present invention have been described above with reference to specific examples. However, the invention is not limited to these specific examples. Based on the above-described embodiment of the present invention, all forms that can be implemented by those skilled in the art by appropriately designing and changing are also included in the scope of the present invention as long as they include the gist of the present invention. In addition, within the scope of the idea of the present invention, those skilled in the art can conceive of various modifications and modifications, and these modifications and modifications also belong to the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Semiconductor element 10... Substrate 11... First surface 12... Second surface 20... Semiconductor layer 30... Sheet 40... Pressing member a, a1 to a4... First modified portion, b, b1 ~ b4... second modified section, c... third modified section, D... dicing street, W... wafer, 51... first electrode, 52... second electrode

Claims (9)

A substrate having a first surface and a second surface is irradiated with a laser beam from the side of the first surface along a first direction parallel to the first surface of the substrate to irradiate the inside of the substrate with a laser beam. a first irradiation step of forming a plurality of first modified portions arranged along one direction and cracks extending from the first modified portions toward at least the first surface;
After the first irradiation step, a laser beam is irradiated from the first surface side to a position shifted in a second direction crossing the first direction and parallel to the first surface from the first modified portion. a second irradiation step of forming a plurality of second modified portions arranged along the first direction at positions adjacent to the plurality of first modified portions in the second direction;
After the second irradiation step, a laser beam is irradiated along the first direction from the first surface side, and the thickness of the substrate is increased from the first modified portion to the first surface side of the first modified portion. a third irradiation step of forming a plurality of third modified portions arranged along the first direction at positions overlapping the plurality of first modified portions in a direction plan view ;
After the third irradiation step, pressing the substrate from the second surface side with a pressing member to cut the substrate;
with
A method of manufacturing a semiconductor device in which a modified portion is not formed at a position adjacent to the third modified portion in the second direction and overlapping the second modified portion in plan view in the thickness direction of the substrate. . 2. The method of manufacturing a semiconductor device according to claim 1, further comprising, after the third irradiation step, a fourth irradiation step of irradiating the same position as the third modified portion with a laser beam from the first surface side. 3. The method of manufacturing a semiconductor device according to claim 1, further comprising a step of preparing a wafer having said substrate and a semiconductor layer provided on said second surface before said first irradiation step. The first reformed section and the third reformed section are arranged such that the distance from the first reformed section to the second surface is greater than the distance from the third reformed section to the first surface. A method for manufacturing a semiconductor device according to any one of claims 1 to 3, wherein the semiconductor element is formed. Before the third irradiation step, the first irradiation step and the second irradiation step are repeated to form a pair of the first modified portion and the second modified portion adjacent in the second direction. 5. The method of manufacturing a semiconductor device according to claim 1, wherein a plurality of pairs are formed in the thickness direction of the substrate. 6. The method of manufacturing a semiconductor device according to claim 5, wherein the closer the pair is to the second surface, the smaller the distance in the second direction between the center of the first modified portion and the center of the second modified portion in the plurality of pairs. . 7. The method of manufacturing a semiconductor device according to claim 5, wherein the first modified portion and the second modified portion are formed by increasing the output of laser light for a pair closer to the second surface among the plurality of pairs. The plurality of pairs of the first reforming section and the second reforming section are composed of the first pair of the first reforming section and the second reforming section and the first pair of the first reforming section. and a second pair of the first reformed section and the second reformed section closer to the second surface than the second reformed section,
irradiating the plurality of pairs of the first modified portion and the second modified portion with a laser beam with a pulse width of 100 fsec to 1000 psec;
The output of the laser light irradiated to the first pair of the first modified portion and the second modified portion has a pulse energy of 7 μJ,
The output of the laser light with which the first modified portion and the second modified portion of the second pair are irradiated is applied to the first modified portion and the second modified portion of the first pair. 8. The method of manufacturing a semiconductor device according to claim 7, wherein the pulse energy is 8 μJ, which is higher than the laser light output. a substrate having a first side, a second side, and at least one side;
a semiconductor layer formed on the second surface;
with
said at least one side of said substrate comprising:
one or more flat regions;
a first region having a surface roughness greater than that of the flat region and extending along a first direction parallel to the first surface at a position away from the first surface and the second surface;
A first surface extending in a first direction parallel to the first surface between the first area and the first surface and away from the first surface and having a surface roughness greater than that of the flat area. 2 regions;
a plurality of substrates arranged along the first direction at positions shifted from the first region in a second direction crossing the first direction and parallel to the first surface within the substrate; A semiconductor device having a modified portion of

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