Method for manufacturing a semiconductor element and semiconductor element

Abstract

Provided are a method for manufacturing a semiconductor element and a semiconductor element, which can suppress a substrate notch when the substrate is cut. The method for manufacturing a semiconductor element includes: a first irradiation process of irradiating a laser from a first surface side to an inside of a substrate to form a plurality of first modification portions arranged along a first direction in the inside of the substrate; a second irradiation process of irradiating a laser to a position deviated from the first modification portions in a second direction to form a plurality of second modification portions arranged along the first direction at positions adjacent to the plurality of first modification portions in the second direction; and a third irradiation process of irradiating a laser from the first surface side along the first direction to form a plurality of third modification portions arranged along the first direction at positions more deviated from the first surface side than the first modification portions and coinciding with the plurality of first modification portions in a thickness direction of the substrate. No modification portion is formed at positions adjacent to the third modification portions in the second direction and coinciding with the second modification portions in the thickness direction of the substrate.

Description

Technical Field

[0001] This invention relates to a method for manufacturing semiconductor devices and semiconductor devices themselves. Background Technology

[0002] Semiconductor devices are typically obtained by dicing a wafer formed by creating a semiconductor layer on a substrate. Known methods for dicing wafers include focusing a laser beam into the interior of the substrate to form a modified region, and then dicing the wafer starting from a crack extending from that modified region. For example, Patent Document 1 describes a laser dicing method in which two parallel rows of modified regions are formed within a dicing path by irradiating the wafer with a laser beam along a first and a second straight line.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-48207

[0006] In the method of Patent Document 1, since cracks are generated from two rows of modified regions to the substrate surface, the substrate may be notched when it is cut. Summary of the Invention

[0007] The purpose of this invention is to provide a method for manufacturing a semiconductor device that can suppress substrate gaps when cutting a substrate, as well as the semiconductor device itself.

[0008] According to one aspect of the present invention, a method for manufacturing a semiconductor element includes the following steps: a first irradiation step, wherein a laser is irradiated from the first surface side toward the interior of the substrate along a first direction parallel to the first surface of a substrate having a first surface and a second surface, thereby forming a plurality of first modified portions arranged along the first direction and a crack extending from the first modified portions toward at least the first surface within the interior of the substrate; a second irradiation step, after the first irradiation step, wherein a laser is irradiated from the first surface side toward a position offset from the first modified portions in a second direction intersecting the first direction and parallel to the first surface, thereby forming a plurality of second modified portions arranged along the first direction at adjacent positions in the second direction of the plurality of first modified portions; a third irradiation step, after the second irradiation step, wherein a laser is irradiated from the first surface side along the first direction, thereby forming a plurality of third modified portions arranged along the first direction at a position further toward the first surface side than the first modified portions and coinciding with the plurality of first modified portions in the thickness direction of the substrate; and a step of cutting the substrate by pressing the substrate from the second surface side using a pressing member after the third irradiation step. No modified portion is formed at a position adjacent to the second modified portion in the second direction of the third modified portion and at a position that coincides with the second modified portion in the thickness direction of the substrate.

[0009] The semiconductor device manufacturing method and semiconductor device according to the present invention can suppress notches in the substrate when cutting the substrate. Attached Figure Description

[0010] Figure 1 This is a schematic top view of the wafer in an embodiment of the present invention.

[0011] Figure 2 This is a schematic cross-sectional view of the wafer in an embodiment of the present invention.

[0012] Figure 3A This is a schematic cross-sectional view showing the first irradiation step in the manufacturing method of a semiconductor element according to the first embodiment of the present invention.

[0013] Figure 3B This is a schematic top view illustrating the first irradiation step in the manufacturing method of a semiconductor element according to the first embodiment of the present invention.

[0014] Figure 4A This is a schematic cross-sectional view showing the second irradiation step in the method for manufacturing a semiconductor element according to the first embodiment of the present invention.

[0015] Figure 4B This is a schematic top view illustrating the second irradiation step in the method for manufacturing a semiconductor element according to the first embodiment of the present invention.

[0016] Figure 5AThis is a schematic cross-sectional view showing the third irradiation step in the method for manufacturing a semiconductor element according to the first embodiment of the present invention.

[0017] Figure 5B This is a schematic top view illustrating the third irradiation step in the manufacturing method of a semiconductor element according to the first embodiment of the present invention.

[0018] Figure 6 This is a schematic cross-sectional view illustrating the cutting process in the manufacturing method of a semiconductor element according to the first embodiment of the present invention.

[0019] Figure 7A This is a schematic top view illustrating the cutting process in the manufacturing method of a semiconductor element according to the first embodiment of the present invention.

[0020] Figure 7B This is a schematic top view illustrating the cutting process in the manufacturing method of a semiconductor element according to the first embodiment of the present invention.

[0021] Figure 8 This is a schematic cross-sectional view showing the laser irradiation step in the semiconductor device manufacturing method according to the second embodiment of the present invention.

[0022] Figure 9 This is a schematic cross-sectional view showing the laser irradiation step in the semiconductor device manufacturing method according to the third embodiment of the present invention.

[0023] Figure 10 This is a schematic cross-sectional view showing the laser irradiation step in the semiconductor device manufacturing method according to the fourth embodiment of the present invention.

[0024] Figure 11 This is a schematic cross-sectional view of a semiconductor device manufactured according to one embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures

[0026] 1: Semiconductor components;

[0027] 10: Substrate;

[0028] 11: First page;

[0029] 12: Second page;

[0030] 20: Semiconductor layer;

[0031] 30: Sheets;

[0032] 40: Pressing component;

[0033] a, a1~a4: First modification part;

[0034] b, b1~b4: Second modification section;

[0035] c: Third modification section;

[0036] D: Cutting track;

[0037] W: wafer;

[0038] 51: First electrode;

[0039] 52: Second electrode. Detailed Implementation

[0040] Hereinafter, embodiments will be described with reference to the accompanying drawings. It is worth noting that in each drawing, the same structures are labeled with the same reference numerals.

[0041] The semiconductor device manufacturing method according to the embodiments of the present invention includes: a wafer preparation process, a laser irradiation process, and a wafer cutting process.

[0042] Figure 1 This is a schematic top view of the wafer W in the embodiment. Figure 2 It is a schematic cross-sectional view of the portion of the wafer W with the dicing lines D formed.

[0043] The wafer W has a substrate 10 and a semiconductor layer 20. The substrate 10 has a first surface 11 and a second surface 12 opposite to the first surface 11. The semiconductor layer 20 is disposed on the second surface 12 of the substrate 10.

[0044] The substrate 10 is, for example, a sapphire substrate. The first surface 11 is, for example, the c-plane of sapphire. It is noteworthy that the first surface 11 can be tilted relative to the c-plane within a range that allows for the formation of a semiconductor layer 20 with good crystallinity. Figure 1 In this context, the X direction and the Y direction represent two mutually perpendicular directions within a plane parallel to the first surface 11 of the substrate 10. For example, the X direction is along the m-axis of the sapphire, and the Y direction is along the a-axis of the sapphire.

[0045] The semiconductor layer contains, for example, In x Ai y Ga 1-x-y N (0≦x, 0≦y, x+y<1) represents a nitride semiconductor. Semiconductor layer 20 includes an active layer. The active layer is, for example, a light-emitting active layer. The peak wavelength of the light emitted by the active layer is, for example, 280 nm or more and 650 nm or less. Alternatively, the peak wavelength of the light emitted by the active layer may be either less than 280 nm or greater than 650 nm.

[0046] Multiple cleavage paths D are formed on the wafer W in a lattice pattern, for example. Cleavage paths D are the boundary regions between multiple semiconductor devices monolithically formed by cutting the wafer W, and are regions whose width is set with a margin (width) that does not affect the semiconductor devices when the wafer W is cut. Furthermore, cleavage paths D are the scanning areas for lasers used to form the modified portions described later within the substrate 10.

[0047] For example, no semiconductor layer 20 is formed on the dicing track D. Multiple semiconductor layers 20 are separated on the second surface 12 of the substrate 10 via the dicing track D. It is worth noting that the semiconductor layers 20 may also be formed on the entire surface of the second surface 12 of the substrate 10 without being separated by the dicing track D.

[0048] The semiconductor device manufacturing method of the embodiment includes a laser irradiation step after the wafer W preparation step.

[0049] While the laser irradiates the interior of the substrate 10 from the first surface 11, it scans along multiple dicing paths D. Figure 1 In the X and Y directions shown, the laser first scans along the cutting path D extending in one direction, and then scans along the cutting path D extending in the other direction.

[0050] The laser is emitted in a pulsed manner, for example. The pulse width can be from 100 fsec to 1000 psec. As the laser source, for example, an Nd:YAG laser, a Ti:sapphire laser, an Nd:YVO4 laser, or an ND:YLF laser can be used. The wavelength of the laser is the wavelength of the light transmitted through the substrate 10. The laser has a peak wavelength, for example, in the range of 500 nm to 1200 nm.

[0051] The laser irradiation process includes a first irradiation step, a second irradiation step, and a third irradiation step.

[0052] [First Implementation Method]

[0053] <First Irradiation Process>

[0054] Figure 3A This is a schematic cross-sectional view showing the first irradiation process in the first embodiment.

[0055] Figure 3B This is a schematic top view showing the first irradiation process in the first embodiment.

[0056] exist Figure 3A and Figure 3B In this process, the scanning direction of the laser is set as a first direction d1. The first direction d1 is a direction parallel to the first surface 11 of the substrate 10. Along... Figure 1 When the laser is scanned in the X direction as shown, the first direction d1 is parallel to the X direction, and along the X direction... Figure 1 When scanning the laser in the Y direction, the first direction d1 is parallel to the Y direction. The direction intersecting the first direction d1 is designated as the second direction d2. For example, the second direction d2 is orthogonal to the first direction d1.

[0057] In the first irradiation step of the first embodiment, a laser is irradiated into the interior of the substrate 10 from the first surface 11 side along the first direction d1. The laser is focused at a predetermined depth inside the substrate 10, and the energy of the laser is concentrated at that location. A modified portion that is more brittle than the portion not irradiated by the laser is formed in the irradiated portion (focusing portion). In addition, for example, the modified portion is a portion with lower light transmittance than the portion not irradiated by the laser. Here, the position set when irradiating the substrate 10 from the first surface 11 side and the actual position where the modified portion is formed may sometimes deviate. In this case, the position of the irradiated laser can be adjusted by taking into account the amount of deviation. The first modified portion a is formed by the first irradiation step. In addition, strain is generated in the first modified portion a, and a crack cr is generated from the first modified portion a by releasing the strain. The crack cr, which extends at least toward the first surface 11, is formed inside the substrate 10 from the first modified portion a. The output (pulse energy) of the laser used to form the first modified part a is 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 even more preferably 2.0 μJ or more and 10.0 μJ or less.

[0058] The laser is discretely scanned along the first direction d1 within the range of the cutting path D, such as... Figure 3B As shown, a plurality of first modified portions a are formed inside the substrate 10 and arranged along a first direction d1. The plurality of first modified portions a are formed discretely, for example, along the first direction d1. Alternatively, a portion of adjacent first modified portions a in the first direction d1 may contact (or overlap) each other, and the plurality of first modified portions may be formed in a continuous line extending in the first direction d1.

[0059] <Second Irradiation Process>

[0060] Figure 4A This is a schematic cross-sectional view showing the second irradiation process in the first embodiment.

[0061] Figure 4B This is a schematic top view illustrating the second irradiation process in the first embodiment.

[0062] A second irradiation process is performed after the first irradiation process. In the second irradiation process, laser light is irradiated from the first surface 11 towards a position offset from the first modified portion a in the second direction d2. Through the second irradiation process, a second modified portion b is formed inside the substrate 10.

[0063] The laser irradiation position in the thickness direction of the substrate 10 during the formation of the second modified portion b is approximately the same as the laser irradiation position in the thickness direction of the substrate 10 during the formation of the first modified portion a. Therefore, the position of the second modified portion b in the thickness direction of the substrate 10 is approximately the same as the position of the first modified portion a in the thickness direction of the substrate 10. "Approximately the same" here means that a deviation of less than 10 μm is permissible, preferably less than 5 μm. The first modified portion a and the second modified portion b are adjacent in the second direction d2 within the range of the cutting kerf D. "The first modified portion a and the second modified portion b are adjacent in the second direction d2 within the range of the cutting kerf D" means that at least a portion of the first modified portion a and the second modified portion b are adjacent to each other in the second direction d2. For example, the first modified portion a and the second modified portion b may be separated in the second direction d2. Alternatively, a portion of the first modified portion a and a portion of the second modified portion may be connected or overlapped in the second direction d2. When a portion of the first modified portion a overlaps with a portion of the second modified portion b, the strength of the region where the modified portion is formed, where the portion of the first modified portion a overlaps with a portion of the second modified portion b, may be higher than the strength of the region where the modified portion is formed, where the portion of the first modified portion a overlaps with a portion of the second modified portion b. Therefore, when the first modified portion a and the second modified portion b are separated in the second direction d2, multiple modified portions are not densely formed inside the substrate 10 because they do not overlap with each other. Therefore, in the wafer W cutting process described later, the force required to cut 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.

[0064] The laser is discretely scanned along the first direction d1 at a position offset from the first modified part d2 in the second direction d2. For example... Figure 4B As shown, a plurality of modified portions b arranged along the first direction d1 are formed at adjacent positions on the second direction d2 of a plurality of first modified portions a arranged along the first direction d1.

[0065] When multiple first modified portions a are discretely formed along a first direction d1, multiple second modified portions b can also be discretely formed along the first direction d1, corresponding to the positions of each first modified portion a in the first direction d1. Furthermore, when multiple first modified portions a are formed in a continuous line extending along the first direction d1, with portions of adjacent first modified portions a connecting (or overlapping) to each other, multiple second modified portions b can also be formed in a continuous line extending along the first direction d1, with portions of adjacent portions connecting (or overlapping) to each other. Either the multiple first modified portions a or the multiple second modified portions b can be formed in a continuous line extending along the first direction d1.

[0066] By forming a second modified portion b at an adjacent position in the second direction d2 of the first modified portion a, the propagation of cracks generated in the first modified portion can be promoted. Cracks are generated from the modified portion due to the release of strain generated during its formation. Furthermore, it is hypothesized that when a new modified portion is formed near the area where a modified portion has been formed and where a crack has already formed, the force generated during strain release acts not only on cracks generated from the newly formed modified portion but also on existing cracks. That is, it is hypothesized that the force generated when strain is released during the formation of the second modified portion b acts on cracks extending from the already formed first modified portion a, thereby promoting the propagation of cracks extending from the first modified portion a toward the first surface 11 of the substrate 10. The output of the laser used to form the second modified portion b is preferably, for example, 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 even more preferably 2.0 μJ or more and 10.0 μJ or less.

[0067] <Third Irradiation Process>

[0068] Figure 5A This is a schematic cross-sectional view showing the third irradiation step in the first embodiment.

[0069] Figure 5B This is a schematic top view showing the third irradiation process in the first embodiment.

[0070] After the second irradiation step, a third irradiation step is performed. In the third irradiation step, laser light is irradiated along the first direction d1 on the first surface 11 of the substrate 10. Through this third irradiation step, a third modified portion c is formed inside the substrate 10. The irradiation position of the laser in the thickness direction of the substrate 10 when forming the third modified portion c is closer to the first surface 11 than the irradiation position of the laser in the thickness direction of the substrate 10 when forming the first modified portion a. 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. Moreover, the third modified portion c is formed in the thickness direction of the substrate 10 at a position coinciding with the first modified portion a. The first modified portion a and the third modified portion c are separated in the thickness direction of the substrate 10.

[0071] In the third irradiation process, the laser is scanned discretely along the first direction d1, and a plurality of third modified portions c are formed at a position that is more biased toward the first surface 11 than the first modified portion a inside the substrate 10 and coincides with a plurality of first modified portions in the thickness direction of the substrate 10.

[0072] When multiple first modified portions a are discretely formed along the first direction d1, multiple third modified portions c can also be discretely formed along the first direction d1. Furthermore, when multiple first modified portions a are formed in a continuous line extending along the first direction d1, with portions of adjacent first modified portions a connecting (or overlapping) to each other, multiple third modified portions c can also be formed in a continuous line extending along the first direction d1, with portions of adjacent portions connecting (or overlapping) to each other. Moreover, either the multiple first modified portions a or the multiple third modified portions c can be formed in a continuous line extending along the first direction d1.

[0073] Strain is generated by forming the third modified portion c, and a crack cr is generated from the third modified portion c by releasing this strain. The third modified portion c is located at a position that coincides with the first modified portion a in the thickness direction of the substrate 10. Therefore, in the case of a crack cr extending from the third modified portion c toward the second surface 12, the crack cr can connect with the crack cr extending from the first modified portion a toward the first surface 11.

[0074] A crack cr extending from the third modified portion c toward the first surface 11 reaches the first surface 11. Alternatively, a crack cr extending from the third modified portion c toward the first surface 11 reaches a position close to the first surface 11. In either case, the crack cr extending from the third modified portion c toward the first surface 11 reaches a position closer to the first surface 11 than a crack cr extending from the second modified portion b toward the first surface 11, which is located further away from the first surface 11 than the third modified portion c (closer to the second surface 12). Cracks extending from the second modified portion do not reach or have difficulty reaching the first surface 11.

[0075] The first, second, and third irradiation processes described above are for... Figure 1 The multiple cutting paths D shown are performed separately.

[0076] <Wafer W Cutting Process>

[0077] After the third irradiation process, the wafer W is cut.

[0078] Figure 6 This is a schematic cross-sectional view showing the dicing process of wafer W.

[0079] The wafer W, with the semiconductor layer 20 side, is bonded to the sheet 30. Then, the substrate 10 is pressed from the second surface 12 side using a pressing member 40, across the sheet 30. The pressing member 40 is, for example, a knife-shaped member extending along the dicing ridge D. The substrate 10, subjected to the pressing pressure of the pressing member 40 from the second surface 12 side, begins to be diced starting from a crack extending from the third modified portion c and reaching or near the first surface 11. That is, a V-shaped groove 15, opening on the first surface 11, is formed along the dicing ridge D, reaching the second surface 12, and the wafer W is cut. It is worth noting that the wafer W can be cut using either the method of starting dicing from a crack extending from the third modified portion c and reaching or near the first surface 11, or other methods.

[0080] For example, the wafer W is first cut along the dicing path D extending in the X direction, as shown below. Figure 7A As shown, the wafer W is separated into multiple rods 50 extending in the X direction.

[0081] Then, along the cutting path D extending in the Y direction, the cutting rod 50 is cut off, as follows: Figure 7B As shown, wafer W is monolithically divided into multiple semiconductor devices 1. It is worth noting that it is also possible to first cut along the Y direction and then cut along the X direction.

[0082] On the sides of each monolithized semiconductor element 1, the modified portions a and c are exposed in areas with a larger surface roughness than the portions without modified portions.

[0083] According to the first embodiment described above, by forming a second modified portion adjacent to the first modified portion a, it is possible to promote the propagation of cracks generated from the first modified portion a toward the first surface 11. Therefore, even thick substrates 10 are easier to cut. 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.

[0084] Within the range of a cutting path D, the distance between the centers of the first modified portion a and the second modified portion b in the second direction d2 is set within a range such that the force when the strain generated during the formation of the second modified portion b is released can act on the crack extending from the already formed first modified portion a, thereby causing the crack extending from the first modified portion a toward the first surface 11 of the substrate 10 to propagate. 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.

[0085] No modified portion is formed at the position adjacent to the third modified portion c in the second direction d2 and overlapping with the second modified portion b in the thickness direction of the substrate 10. Within the range of a cutting path D, there is no modified portion at the position adjacent to the third modified portion c in the second direction d2. There is no modified portion at the position adjacent to the third modified portion c in the second direction d2 and overlapping with the position from the first modified portion a to the second modified portion b in the thickness direction of the substrate 10.

[0086] Therefore, cracks from the third modified portion c reaching or near the first surface 11 are unlikely to form at adjacent positions in the second direction d2, thus preventing them from reaching or near the first surface 11. Cracks from the second modified portion b do not reach positions closer to the first surface 11 than cracks from the third modified portion c. Within the range of a cutting path D, limiting cracks reaching or near the first surface 11 to cracks extending from the third modified portion c reduces the number of cracks that facilitate cutting from the first surface 11 side. For example, cracks that facilitate cutting from the first surface 11 side can be limited to a single crack extending from the third modified portion c. Thus, while easily forming cracks extending towards the first surface 11, it also suppresses the formation of gaps in the substrate 10 when cutting from the first surface 11 side.

[0087] After the third irradiation step, a fourth irradiation step can be performed where laser is irradiated from the first surface 11 side under conditions that allow for the formation of a modified portion. The fourth irradiation step involves irradiating the same location as the third modified portion c with laser. This fourth irradiation step promotes the propagation 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. Even in this case, because no modified portion is formed at a location adjacent to the third modified portion c in the second direction d2, cracks reaching the first surface within the range of a cutting path D can be limited to cracks extending from the third modified portion c, thus suppressing notches in the substrate 10. The conditions for forming a modified portion are, for example, the same conditions as the third irradiation step. At the same location as the third modified portion, through the fourth irradiation step, sometimes part or all of the third modified portion remains unmodified, and sometimes part or all of it is further modified. Furthermore, sometimes a new modified portion is formed in addition to the third modified portion.

[0088] Since a semiconductor 20 is disposed on the second surface 12 of the substrate 10, in order to suppress thermal damage to the semiconductor layer 20 caused by laser irradiation, the laser irradiation position in the first irradiation process is preferably a position at or above a predetermined distance (a distance from which the semiconductor layer 20 is not subject to thermal damage) from the second surface 12.

[0089] Furthermore, since the pressing member 40 applies pressing pressure from the second surface 12 side and the division begins from the first surface 11 side, if the third modified part c approaches the first surface 11, the crack from the third modified part c can easily reach the first surface 11 and be easily cut off.

[0090] Therefore, the preferred option is as follows: Figure 5A As shown, the first modified portion a and the third modified portion c are formed such 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. 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, when the thickness of the substrate 10 is 300 mm or less, it is preferable to form the first modified portion a and the third modified portion c such 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.

[0091] [Second Implementation]

[0092] Figure 8 This is a schematic cross-sectional view illustrating the laser irradiation process of a semiconductor element manufacturing method according to a second embodiment of the present invention.

[0093] In this embodiment, before the third irradiation step, the first irradiation step and the second irradiation step are repeated to form multiple pairs of first modified portions and second modified portions that are adjacent in the second direction d2 in the thickness direction of the substrate 10.

[0094] At the position closest to the second surface 12, a first pair of first modified portions 1 and second modified portions b1 adjacent in the second direction d2 are formed. At a position closer to the first surface 11 than the first pair, a second pair of first modified portions a2 and second modified portions b2 adjacent in the second direction d2 are formed. At a position closer to the first surface 11 than the second pair, a third pair of first modified portions a3 and second modified portions b3 adjacent in the second direction d2 are formed. At a position closer to the first surface 11 than the third pair, a fourth pair of first modified portions a4 and second modified portions b4 adjacent in the second direction d2 are formed. Each pair is arranged along the first direction d1 in the same manner as the first modified portions a and second modified portions b in the first embodiment.

[0095] The third modified portion c is formed closer to the first surface 1 than the first modified portion a4 of the fourth pair. The third modified portion c coincides with the first modified portions a1 to a4 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 located on the same line in the thickness direction of the substrate 10. Figure 8 (Using imaginary dots and dashes to represent the middle part).

[0096] The second modified portions b1 to b4 coincide in the thickness direction of the substrate 10, and the centers of each of the second modified portions b1 to b4 are located on the same line (in Figure 8 (Using imaginary dots and dashes to represent the middle part).

[0097] The first and second irradiation processes, each reaching the same depth, are performed consecutively, with deeper modified sections forming earlier. That is, the first and second irradiation processes are repeated alternately, sequentially forming the first modified section a1, the second modified section b1, the first modified section a2, the second modified section b2, the first modified section a3, the second modified section b3, the first modified section a4, and the second modified section b4. Subsequently, the third modified section c is formed through a third irradiation process.

[0098] In the second embodiment, no modified portion is formed at a position adjacent to the third modified portion c in the second direction d2 and overlapping with the second modified portions b1 to b4 in the thickness direction of the substrate 10.

[0099] According to the second embodiment, by forming multiple pairs of first modified portions a1 to a4 and second modified portions b1 to b4 in the thickness direction of the substrate 10, even for thick substrates 10, cracks can easily extend in the thickness direction of the substrate 10, making it easy to cut. Furthermore, by not forming modified portions at positions adjacent to the third modified portion c in the second direction d2 and coinciding with the second modified portions b1 to b4 in the thickness direction of the substrate 10, gaps in the substrate 10 when it is divided starting from the first surface 11 side are suppressed.

[0100] When the output of a laser irradiating the interior of the substrate 10 from the first surface 11 is constant in the thickness direction of the substrate 10, the energy of the laser focusing portion decreases more easily at positions farther from the first surface 11 due to absorption within the substrate 10. As a result, among the multiple pairs of first modified portions a1-a4 and second modified portions b1-b4, the pairs farther from the first surface 11 (closer to the second surface 12) tend to have smaller modified portion sizes. Therefore, as... Figure 8 As shown, the farther away from the first surface 11, the greater the distance between the first modified portions a1-a4 and the second modified portions b1-b4 in the second direction d2. That is, the farther away from the first surface 11 a pair is, the weaker the effect of the second modified portions b1-b4 on promoting crack propagation in the adjacent first modified portions a1-a4. In the second embodiment, the shortest distance in the second direction d2 between the pair of first modified portions closest to the third modified portion c and the pair of second modified portions is preferably 0.1 μm or more and 2 μm or less. In addition, the shortest distance in the second direction d2 between the pair of first modified portions farthest from the first surface 11 and the pair of second modified portions is preferably 0.1 μm or more and 6 μm or less. By designing the distance range in the second direction d2 between the pair of first modified portions farthest from the first surface 11 and the pair of second modified portions, it is possible to make the second modified portion more likely to influence the crack propagation promotion of the first modified portion.

[0101] [Third Implementation Method]

[0102] Figure 9 This is a schematic cross-sectional view illustrating the laser irradiation step in a method for manufacturing a semiconductor device according to a third embodiment of the present invention. Figure 9 The dashed line is used to represent a line that passes through the center of each modified part in the second direction and extends along the thickness direction of the substrate 10.

[0103] The third embodiment is similar to the following aspects. Figure 8 The second embodiment shown is different. That is, in the third embodiment, among the multiple pairs of first modified portions a1 to a4 and second modified portions b1 to b4, the closer to the second surface 12, the smaller the distance between the center of the first modified portion a1 to a4 and the center of the second modified portion b1 to b4 in the second direction.

[0104] In the third embodiment, during the second irradiation process of forming the second modified portions b1 to b4, the laser irradiation position (focusing position) is brought closer to the first modified portions a1 to a4 at positions further away from the first surface 11 where the size of the second modified portions b1 to b4 is easily reduced. The output of the laser irradiating into the interior of the substrate 10 from the first surface 11 side is constant in the thickness direction of the substrate 10. As a result, the variation in the distance between the first modified portions a1 to a4 and the second modified portions b1 to b4 in the second direction d2 in the thickness direction of the substrate 10 is reduced, thereby weakening the effect of promoting crack propagation in the adjacent first modified portions in the second modified portions far from the first surface 11.

[0105] [Fourth Implementation Method]

[0106] Figure 10 This is a schematic cross-sectional view of the laser irradiation step in the semiconductor device manufacturing method according to the fourth embodiment of the present invention. Figure 10 The dashed line is used to represent the line that passes through the center of each modified part in the second direction d2 and extends along the thickness direction of the substrate 10.

[0107] The fourth embodiment is the same as the second embodiment except that the first modified portions a1 to a4 and the second modified portions b1 to b4 are formed in such a way that the laser output is higher for the pair closer to the second surface 12 among the multiple pairs of the first modified portions a1 to a4 and the second modified portions b1 to b4.

[0108] The further away from the first surface 11, the lower the energy of the laser focusing section becomes, making it easier for insufficient energy to propagate cracks from the first modified sections a1 to a4 and insufficient energy for the second modified sections b1 to b4 to promote crack propagation in adjacent first modified sections a1 to a4. Therefore, in the fourth embodiment, the first modified sections a1 to a4 and the second modified sections b1 to b4 are formed in such a way that the laser output is maximized the further away from the first surface 11. As a result, insufficient crack propagation at locations far from the first surface 11 can be suppressed.

[0109] exist Figures 8-10In the second to fourth embodiments shown, for example, the substrate 10 has a thickness of 700 μm. A first modified portion a1 and a second modified portion b1 are formed at a distance of 550 μm from the first surface 11; a first modified portion a2 and a second modified portion b2 are formed at a distance of 420 μm from the first surface 11; a first modified portion a3 and a second modified portion b3 are formed at a distance of 300 μm from the first surface 11; a first modified portion a4 and a second modified portion b4 are formed at a distance of 210 μm from the first surface 11; and a third modified portion c is formed at a distance of 120 μm from the first surface 11. Here, the position set when irradiating the substrate 10 with laser from the first surface 11 side sometimes deviates from the actual position where the modified portions are formed. In this case, the position of the irradiated laser can be adjusted by taking into account the amount of deviation.

[0110] In the second and third embodiments, the laser output used to form 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.

[0111] In the fourth embodiment, for example, the laser output for forming the third modified portion is 6.0 μJ, the laser output for forming the first modified portion a4 and the second modified portion b4 is 7.0 μJ, the laser output for forming the first modified portion a3 and the second modified portion b3 is 8.0 μJ, the laser output for forming the first modified portion a2 and the second modified portion b2 is 9.0 μJ, and the laser output for forming the first modified portion a1 and the second modified portion b1 is 10.0 μJ.

[0112] In the second and fourth embodiments, the center-to-center distance between the first modified part a1 and the second modified part b1 in the second direction d2, the center-to-center distance between the first modified part a2 and the second modified part b2 in the second direction d2, the center-to-center distance between the first modified part a3 and the second modified part b3 in the second direction d2, and the center-to-center distance between the first modified part a4 and the second modified part b4 in the second direction d2 are, for example, 6.0 μm.

[0113] In the third embodiment, for example, the center-to-center distance between the first modified part a1 and the second modified part b1 in the second direction d2 is 4.0 μm, the center-to-center distance between the first modified part a2 and the second modified part b2 in the second direction d2 is 4.5 μm, the center-to-center distance between the first modified part a3 and the second modified part b3 in the second direction d2 is 5.0 μm, and the center-to-center distance between the first modified part a4 and the second modified part b4 in the second direction d2 is 5.5 μm.

[0114] exist Figures 8-10In the second to fourth embodiments shown, after the third irradiation process, a fourth irradiation process may be performed to irradiate a laser from the first surface 11 side to a position that coincides with the third modified part c.

[0115] Furthermore, in the second to fourth embodiments, the first modified portions a1 to a4 and the third modified portion c are formed such that the distance from the first modified portion a1, which is closest to the second surface 12, to the second surface 12 is greater than the distance from the third modified portion c to the first surface 11. This can suppress thermal damage to the semiconductor layer caused by laser irradiation and make it easier for cracks to reach the first surface 11 from the third modified portion and be easily cut off.

[0116] 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, but there may also be two, three, or five or more pairs that overlap in the thickness direction of the substrate 10.

[0117] Furthermore, in the first to fourth embodiments, it is preferable that no other modified portions are formed between the third modified portion c and the first surface 11. Additionally, it is preferable that no other modified portions are formed between the third modified portion c and the first modified portion a, or between the third modified portion c and the second modified portion b.

[0118] exist Figure 11 The image shows a cross-sectional view of a semiconductor element 1 manufactured according to an embodiment of the present invention. Figure 11 The semiconductor element 1 shown includes a first surface 11 of a substrate 10, a second surface 12 opposite to the first surface 11, a semiconductor layer 20 formed on the second surface 12, and a first electrode 51 and a second electrode 52 formed on the semiconductor layer 20. Furthermore, the semiconductor layer 20 sequentially comprises a first semiconductor layer 201, an active layer 202, and a third semiconductor layer 203 from the second surface 12 side. The active layer 202 is also referred to as 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. On the side surface of the substrate 10, there is a first region where modified portion a is exposed and a second region where modified portion c is exposed. For example, in the substrate 10, the modified portion is the portion with lower light transmittance than the portion without modified portion. The first region is located at a position away from the first surface 11 and the second surface 12, along a first direction parallel to the first surface 11 (…). Figure 11The first region extends along the first direction (through the paper). 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. The 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 relatively small surface roughness, and the surface roughness of the first region and the second region is larger than the surface roughness of the flat region. The surface roughness of the side surface of the substrate 10 can be measured, for example, using 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 surface roughness Rz of the flat region is 0.1 μm or more and 2.5 μm or less. In addition, at a position adjacent to the modified portion a on one side surface of the substrate 10, a modified portion b is formed inside the substrate 10, and a plurality of modified portions b are arranged inside the substrate 10 at a position deviating from the first region along the first direction in a second direction that intersects the first direction and is parallel to the first surface. At a position adjacent to the modified portion a on the other side surface of the substrate 10, no modified portion b is formed inside the substrate 10.

[0119] The embodiments of the present invention have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. Based on the above embodiments of the present invention, all methods that can be implemented by those skilled in the art through appropriate design changes, as long as they contain the main content of the present invention, fall within the scope of the present invention. Furthermore, within the scope of the concept of the present invention, those skilled in the art may conceive of various modifications and alterations, which also fall within the scope of the present invention.

Claims

1. A method for manufacturing a semiconductor element, wherein, The method includes: a first irradiation process of irradiating laser light from a first surface side of a substrate along a first direction parallel to the first surface to an inside of the substrate to form a plurality of first modification portions arranged along the first direction and a crack extending from the first modification portions toward at least the first surface in the inside of the substrate; a second irradiation process of irradiating laser light from the first surface side to a position deviated from the first modification portions in a second direction intersecting the first direction and parallel to the first surface after the first irradiation process to form a plurality of second modification portions arranged along the first direction at positions adjacent to the second direction of the plurality of first modification portions; a third irradiation process of irradiating laser light from the first surface side along the first direction after the second irradiation process to form a plurality of third modification portions arranged along the first direction at positions deviated from the first modification portions toward the first surface side and coinciding with the plurality of first modification portions in a thickness direction of the substrate; a process of cutting the substrate by pressing the substrate from a second surface side with a pressing member after the third irradiation process; a position adjacent to the second direction of the third modification portion and coinciding with the second modification portion in the thickness direction of the substrate is not formed with a modification portion.

2. The method for manufacturing a semiconductor element according to claim 1, wherein The method includes a fourth irradiation process of irradiating laser light from the first surface side to the same position as the third modification portion after the third irradiation process.

3. The method for manufacturing a semiconductor element according to claim 1 or 2, wherein The method includes a process of preparing a wafer having the substrate and a semiconductor layer provided on the second surface before the first irradiation process.

4. The method for manufacturing a semiconductor element according to claim 1 or 2, wherein The first modification portion and the third modification portion are formed in a manner such that a distance from the first modification portion to the second surface is greater than a distance from the third modification portion to the first surface.

5. The method for manufacturing a semiconductor element according to claim 1 or 2, wherein The first irradiation process and the second irradiation process are repeated before the third irradiation process to form a plurality of pairs of the first modification portion and the second modification portion adjacent to each other in the second direction in the thickness direction of the substrate.

6. The method for manufacturing a semiconductor element according to claim 5, wherein In the plurality of pairs, the closer a pair is to the second surface, the smaller a distance between a center of the first modification portion and a center of the second modification portion in the second direction.

7. The method for manufacturing a semiconductor element according to claim 5, wherein The first modification portion and the second modification portion are formed in a manner such that the higher an output of laser light is, the closer a pair is to the second surface in the plurality of pairs.

8. The method for manufacturing a semiconductor element according to claim 7, wherein The first modification portion and the second modification portion of the plurality of pairs include the first modification portion and the second modification portion of a first pair and the first modification portion and the second modification portion of a second pair closer to the second surface than the first modification portion and the second modification portion of the first pair, laser light is irradiated to the first modification portion and the second modification portion of the plurality of pairs with a pulse width of 100 fsec to 1000 psec, The output of the laser irradiated to the first modification portion and the second modification portion of the first pair is 7 μ pulse energy of J, The output of the laser irradiated to the first modification portion and the second modification portion of the second pair is higher than the output of the laser irradiated to the first modification portion and the second modification portion of the first pair, and is 8 μ The pulse energy of J.

9. A semiconductor device, wherein, The method includes: a substrate having a first surface, a second surface on an opposite side of the first surface, and at least one side surface; a semiconductor layer formed on the second surface; the substrate has: a first modification portion disposed on the at least one side surface and located in a first region; a third modified portion located more on the first surface side than the first modified portion and located in a second region; and a second modified portion disposed at a position adjacent to the first modified portion inside the substrate, the first region extends in a first direction parallel to the first surface at a position away from the first surface and the second surface, the second region extends in the first direction at a position between the first region and the first surface and away from the first surface, the substrate has no modified portion at a position adjacent to the third modified portion in a second direction inside the substrate and at a position coinciding with the second modified portion in a thickness direction of the substrate, the second direction intersecting the first direction and being parallel to the first surface.

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