Semiconductor device manufacturing method

Abstract

To provide a semiconductor device manufacturing method that can reduce the degradation of semiconductor device quality. [Solution] The laser irradiation process includes a first irradiation step of forming a plurality of modified portions in a sapphire substrate along a first direction. The first irradiation step includes a first step of forming a plurality of first modified portions along a first direction, and a second step of forming a plurality of second modified portions along a first direction after the first step, at a position closer to the second surface of the sapphire substrate than the first modified portions, and at a position that overlaps the first modified portions in a plan view. The amount of aberration correction of the laser light in the first step is smaller than the amount of aberration correction of the laser light in the second step, and the pulse energy of the laser light in the first step is smaller than the pulse energy of the laser light in the second step.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a semiconductor device.

Background Art

[0002] Generally, a semiconductor device is obtained by dicing a wafer in which a semiconductor layer is formed on a substrate. As a method for dicing a wafer, for example, as disclosed in Patent Document 1, a method of condensing a laser beam inside the substrate to form a modified region and dividing the wafer starting from a crack extending from this modified region is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present disclosure is to provide a method for manufacturing a semiconductor device that can reduce a decrease in the quality of the semiconductor device.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, a method for manufacturing a semiconductor device comprises the steps of: preparing a wafer having a sapphire substrate having a first surface and a second surface located opposite to the first surface, and a semiconductor layer disposed on the first surface; a laser light irradiation step of irradiating the interior of the sapphire substrate with laser light from the second surface side; and a separation step of separating the wafer into a plurality of semiconductor devices after the laser light irradiation step, wherein the laser light irradiation step is a first irradiation step of irradiating the laser light along a first direction to form a plurality of modified parts in the interior of the sapphire substrate along the first direction. The first irradiation step comprises a first step of forming a plurality of first modified portions along the first direction, and a second step after the first step of forming a plurality of second modified portions along the first direction at a position closer to the second surface than the first modified portions and overlapping the first modified portions in a plan view, wherein the amount of aberration correction of the laser light in the first step is smaller than the amount of aberration correction of the laser light in the second step, and the pulse energy of the laser light in the first step is smaller than the pulse energy of the laser light in the second step. [Effects of the Invention]

[0006] According to this disclosure, it is possible to provide a method for manufacturing semiconductor devices that can reduce the degradation of semiconductor device quality. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 2] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 3] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 4] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 5] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 6] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 7] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 8] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 9] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 10] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 11] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 12] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 13] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 14] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 15] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 16] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 17] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 18] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 19] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 20] This is a schematic plan view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 21]It is a schematic plan view for explaining one step of a method for manufacturing a semiconductor device according to an embodiment.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, with reference to the drawings, a method for manufacturing a semiconductor device and a semiconductor device according to embodiments of the present disclosure will be described. The following embodiments exemplify a method for manufacturing a semiconductor device for embodying the technical idea of the present embodiment, and are not limited thereto. In addition, dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are not intended to limit the scope of the present disclosure only thereto, but are merely illustrative examples, unless otherwise specified. Note that the sizes, positional relationships, etc. of the members shown in each drawing may be exaggerated for clarity of explanation. In the following description, the same names and reference numerals denote the same or similar members, and detailed descriptions thereof will be omitted as appropriate.

[0009] In the following description, terms indicating a specific direction or position (for example, "up", "down", and other terms including those terms) may be used. However, those terms are merely used for ease of understanding of the relative direction or position in the referenced drawings. As long as the relative direction or position relationship by terms such as "up", "down", etc. in the referenced drawings is the same, in drawings other than the present disclosure, actual products, etc., they do not have to be arranged in the same way as in the referenced drawings. The positional relationship expressed as "up (or down)" in this specification includes, for example, the case where two members are in contact and the case where two members are not in contact and one member is located above (or below) the other member when assuming that there are two members. In addition, in this specification, the width, distance, thickness, and length of a member in a specific direction represent the maximum values of the width, distance, thickness, and length in the specific direction, respectively.

[0010] The method for manufacturing a semiconductor device according to an embodiment includes a step of preparing a wafer, a laser light irradiation step, and a separation step of separating the wafer into a plurality of semiconductor devices. Hereinafter, each step will be described.

[0011] [Wafer preparation process] Figure 1 is a plan view of wafer W. Figure 2 is a schematic cross-sectional view partially showing a cross-section of wafer W.

[0012] The wafer W has a sapphire substrate 10. The sapphire substrate 10 has a first surface 10A and a second surface 10B located on the opposite side of the first surface 10A in the thickness direction Z of the sapphire substrate 10. The thickness of the sapphire substrate 10 is, for example, 400 μm or more and 1000 μm or less.

[0013] The first direction X and the second direction Y are two orthogonal directions within a plane parallel to the first surface 10A or the second surface 10B of the sapphire substrate 10. The first direction X and the second direction Y are orthogonal to the thickness direction Z of the sapphire substrate 10.

[0014] In this embodiment, for example, the first direction X is the direction along the m-axis of the sapphire substrate 10, and the second direction Y is the direction along the a-axis of the sapphire substrate 10. The orientation flat 90 of the sapphire substrate 10 shown in Figure 1 is a plane parallel to the a-plane of the sapphire substrate 10. The cross-sections shown in the drawings of this disclosure are cross-sections perpendicular to the first direction X or the second direction Y. Figure 2 shows a cross-section perpendicular to the first direction X.

[0015] The wafer W has a semiconductor layer 20 disposed on a first surface 10A. The first surface 10A is, for example, the c-plane of the sapphire substrate 10. The first surface 10A may be tilted with respect to the c-plane of the sapphire substrate 10 to a degree that allows for the formation of the semiconductor layer 20 with good crystallinity.

[0016] In this embodiment, the semiconductor element is, for example, a light-emitting element, and the semiconductor layer 20 includes an active layer that emits light. The semiconductor layer 20 is, for example, In x Al y Ga 1-x-y The semiconductor includes a nitride semiconductor represented by N(0≦x≦1,0≦y≦1,x+y≦1). The peak wavelength of light emitted by the active layer of the semiconductor layer 20 is, for example, 200 nm to 600 nm. In this embodiment, the active layer of the semiconductor layer 20 emits, for example, ultraviolet light.

[0017] On the first surface 10A side of the sapphire substrate 10, conductive members electrically connected to the semiconductor layer 20, a protective film covering the semiconductor layer 20, and other such elements may be further arranged.

[0018] In the process of forming the modified portion, which will be described later, laser light is irradiated onto the sapphire substrate 10 along the dicing region 100 of the sapphire substrate 10. In this embodiment, a plurality of dicing regions 100 extend along the first direction X and the second direction Y.

[0019] The dicing region 100 is the region between multiple semiconductor elements that are separated into individual pieces by cleaving the sapphire substrate 10. The width of the dicing region 100 in plan view is set to a width that minimizes the impact on the semiconductor elements due to shifts in the cleavage position of the sapphire substrate 10. In this embodiment, no semiconductor layer 20 is placed on the first surface 10A of the dicing region 100. However, a semiconductor layer 20 may be placed on the first surface 10A of the dicing region 100. The width of the dicing region 100 in a direction perpendicular to the direction in which the dicing region 100 extends is, for example, 10 μm or more and 100 μm or less. The cross-sectional view of this application shows a cross-section cut at the position of the dicing region 100. Figure 2 shows a cross-section cut at the position of the dicing region 100 extending in the second direction Y, and represents a cross-section of a region including two dicing regions 100 extending in the first direction X.

[0020] [Laser light irradiation process] In the laser irradiation process, laser light is irradiated into the interior of the sapphire substrate 10 from the second surface 10B side. The laser light is focused at a predetermined distance from the second surface 10B inside the sapphire substrate 10, and the energy of the laser light is concentrated at that position. A modified region is formed in the area inside the sapphire substrate 10 where the laser light is focused. At least one of the density, refractive index, and mechanical strength in the modified region differs from at least one of the density, refractive index, and mechanical strength in the unmodified region surrounding the modified region. Multiple cracks may originate from a single modified region in multiple directions. Cracks may also branch off from a single crack.

[0021] The laser light is emitted in pulses, for example. The pulse width of the laser light is, for example, between 100 femtoseconds and 1000 picoseconds. As the laser light source, for example, an Nd:YAG laser, a titanium-sapphire laser, an Nd:YVO4 laser, or an Nd:YLF laser can be used. The wavelength of the laser light is the wavelength of light that passes through the sapphire substrate 10. The laser light has a peak wavelength in the range of, for example, 500 nm to 1200 nm.

[0022] <First irradiation process> The laser irradiation process includes a first irradiation step in which laser light is irradiated along a first direction X to form a plurality of modified regions within the sapphire substrate 10 along the first direction X. In the first irradiation step, the laser light is irradiated along each of the plurality of dicing regions 100 that extend in the first direction X.

[0023] The first irradiation process will be described with reference to Figures 3 to 13. Figures 3, 6, 9, 10, and 12 show YZ cross-sections perpendicular to the first direction X. Figures 4, 7, and 13 show XZ cross-sections parallel to the first direction X. Figures 5, 8, and 11 are plan views of the second surface 10B of the wafer W viewed from the positive direction of the Z axis.

[0024] (1st step) The first irradiation step includes a first step of forming a plurality of first modified portions 11 along a first direction X, as shown in Figures 3 to 5.

[0025] As shown in Figures 4 and 5, for example, parts of adjacent first modified portions 11 in the first direction X may be in contact with or overlap each other. Adjacent first modified portions 11 in the first direction X may be formed separately from each other in the first direction X.

[0026] (2nd process) The first irradiation step further includes a second step, after the first step, in which a plurality of second modified portions 12 are formed along a first direction X. As shown in Figures 6 to 8, in the second step, the second modified portions 12 are formed at a position closer to the second surface 10B than the first modified portion 11, and at a position that overlaps with the first modified portion 11 in a plan view. In a plan view, the second modified portions 12 and the first modified portion 11 overlap at least partially.

[0027] As shown in Figures 6 and 7, the second modified portion 12 is located between the first modified portion 11 and the second surface 10B in the thickness direction Z of the sapphire substrate 10. The first modified portion 11 is located between the second modified portion 12 and the first surface 10A in the thickness direction Z of the sapphire substrate 10, and is located closer to the semiconductor layer 20 than the second modified portion 12. In the thickness direction Z of the sapphire substrate 10, the second modified portion 12 is not in contact with the first modified portion 11. Cracks extending from the first modified portion 11 and cracks extending from the second modified portion 12 can be connected.

[0028] As shown in Figures 7 and 8, for example, adjacent second modified portions 12 in the first direction X are formed apart from each other. Parts of adjacent second modified portions 12 in the first direction X may be in contact with or overlap each other.

[0029] During irradiation with laser light to form a modified portion, aberrations may occur at the focusing position of the laser light within the sapphire substrate 10 due to the refractive index difference between air and the second surface 10B of the sapphire substrate 10. Aberration is a phenomenon in which the light rays constituting the laser light do not converge to a single point but instead scatter. This aberration can be corrected with a spatial light phase modulator. As a spatial light phase modulator, for example, a spatial light phase modulator including a liquid crystal layer on which a predetermined modulation pattern is displayed can be used.

[0030] The ideal focusing state is defined as the state in which aberrations are reduced to the point where they are close to the focusing state assuming there is no medium (sapphire substrate in this embodiment) after aberration correction has been performed to cancel out the aberrations that occur at the focusing position of the laser beam. The amount of aberration correction required to achieve the ideal focusing state in the medium is defined as the ideal aberration correction amount. The state in which aberration correction has been performed to cancel out aberrations in order to approach the ideal focusing state is defined as the weakly corrected focusing state. The amount of aberration correction in the weakly corrected focusing state is smaller than the ideal aberration correction amount.

[0031] When the aberration correction amount is small, the region where the energy required to form the modified area is concentrated becomes smaller, making it more difficult for cracks to extend from the modified area. Therefore, among the cracks extending in multiple directions from each modified area, cracks are less likely to connect in directions other than the first direction X, and the meandering of cracks in the first direction X can be reduced. According to this embodiment, the aberration correction amount of the laser light in the first step is smaller than the aberration correction amount of the laser light in the second step. Therefore, cracks from the first modified area 11 are less likely to meander in the first direction X than cracks from the second modified area 12. Since the first modified area 11 is located closer to the semiconductor layer 20 than the second modified area 12, reducing the meandering of cracks from the first modified area 11 can reduce the impact of cracks on the semiconductor layer 20. This makes it possible to stabilize the shape of the semiconductor layer 20. For example, the aberration correction amount of the laser light in the first step is a weak aberration correction amount, and the aberration correction amount of the laser light in the second step is an ideal aberration correction amount.

[0032] If the aberration correction amount is small, the focusing ability of the laser beam deteriorates, and a large amount of light tends to pass through to the first surface 10A side without contributing to the formation of the modified area. Light that passes through to the first surface 10A side can damage the semiconductor layer 20 located on the first surface 10A. According to this embodiment, the pulse energy of the laser beam in the first step is smaller than the pulse energy of the laser beam in the second step. By making the pulse energy of the laser beam in the first step, where the focusing position of the laser beam is closer to the semiconductor layer 20 than in the second step, and furthermore, where the aberration correction amount is smaller than in the second step and a large amount of pass-through light tends to occur, smaller than the pulse energy of the laser beam in the second step, the amount of light that passes through to the first surface 10A side can be reduced, and damage to the semiconductor layer 20 can be reduced.

[0033] The pulse energy of the laser light in the first step is preferably, for example, 1.5 μJ or more and 5.7 μJ or less, more preferably 2.0 μJ or more and 5.2 μJ or less, and still more preferably 2.5 μJ or more and 5.0 μJ or less. The pulse energy of the laser light in the second step is preferably, for example, 4.3 μJ or more and 10.0 μJ or less, more preferably 5.2 μJ or more and 9.2 μJ or less, and still more preferably 5.7 μJ or more and 8.6 μJ or less.

[0034] Since the pulse energy of the laser light in the first step is smaller than the pulse energy of the laser light in the second step, cracks from the first modified section 11 are less likely to extend compared to cracks from the second modified section 12. For this reason, it is preferable to make the irradiation interval of the laser light along the first direction X in the first step smaller than the irradiation interval of the laser light along the first direction X in the second step. This makes it easier for cracks from the first modified section 11 to connect in the first direction X.

[0035] The irradiation interval of the laser light in the first step is preferably, for example, 1.0 μm to 9.0 μm, more preferably 2.0 μm to 8.0 μm, and even more preferably 3.0 μm to 7.0 μm. The irradiation interval of the laser light in the second step is preferably, for example, 6.0 μm to 17.0 μm, more preferably 7.0 μm to 16.0 μm, and even more preferably 8.0 μm to 15.0 μm. The irradiation interval of the laser light can be set, for example, by the scanning speed and frequency of the laser light.

[0036] The second step may be performed multiple times at different locations in the thickness direction Z of the sapphire substrate 10 to form multiple second modified portions 12 that are spaced apart from each other in the thickness direction Z of the sapphire substrate 10, as shown in Figure 9. The multiple second modified portions 12 are formed between the first modified portion 11 and the second surface 10B in the thickness direction Z of the sapphire substrate 10. The multiple second modified portions 12 do not touch each other in the thickness direction Z of the sapphire substrate 10. The multiple second modified portions 12 formed at different locations in the thickness direction Z of the sapphire substrate 10 overlap at least partially in a plan view. Cracks extending from each of the multiple second modified portions 12 can be connected to each other.

[0037] The amount of laser beam aberration correction in the first step is smaller than the amount of laser beam aberration correction in any of the multiple second steps performed at different locations in the thickness direction of the sapphire substrate 10.

[0038] Furthermore, the pulse energy of the laser light in the first step is smaller than the pulse energy of the laser light in any of the multiple second steps performed at different locations in the thickness direction of the sapphire substrate 10.

[0039] Furthermore, the irradiation interval of the laser beam along the first direction X in the first step is smaller than the irradiation interval of the laser beam along the first direction X in any of the multiple second steps performed at different locations in the thickness direction of the sapphire substrate 10.

[0040] (5th step) In this embodiment, the first irradiation step may further include a fifth step of forming a fifth modified portion 15 adjacent to the second modified portion 12 in the second direction Y, as shown in Figures 10 and 11. However, the fifth step is optional.

[0041] As shown in Figure 11, multiple fifth modified portions 15 are formed along the first direction X adjacent to the second direction Y of the second modified portion 12. Adjacent fifth modified portions 15 in the first direction X are formed apart from each other in the first direction X. Parts of adjacent fifth modified portions 15 in the first direction X may touch or overlap.

[0042] When a plurality of second modified portions 12 are formed in the thickness direction Z of the sapphire substrate 10, a fifth modified portion 15 is formed next to at least one of the plurality of second modified portions 12 in the thickness direction Z.

[0043] As shown in Figure 10, the second modified portion 12 and the fifth modified portion 15 are adjacent within the width of the dicing region 100. In this embodiment, as shown in Figure 11, the first modified portion 11, the second modified portion 12, and the fifth modified portion 15 do not overlap the semiconductor layer 20 in a plan view.

[0044] By forming a fifth modified section 15 next to the second modified section 12, the extension of cracks originating from the second modified section 12 can be accelerated. Cracks arise from the modified section when the strain generated during its formation is released. When a new modified section is formed near an area where a modified section has already been formed and cracks have already occurred, it is presumed that the force generated when the strain is released will act not only on cracks newly arising from the newly formed modified section, but also on cracks that have already occurred. In other words, it is presumed that the force generated when the strain generated when the fifth modified section 15 is formed is released acts on cracks extending from the already formed second modified section 12, thereby accelerating the extension of cracks originating from the second modified section 12. As a result, in the process of cutting the sapphire substrate 10 described later, it becomes easier to cut the sapphire substrate 10 even when it is relatively thick.

[0045] The distance in the second direction Y between the adjacent second modified portion 12 and fifth modified portion 15 is preferably, for example, 2 μm or more and 10 μm or less. This makes it easier for the force released when the strain generated when forming the fifth modified portion 15 is released to act on cracks extending from the already formed second modified portion 12. Here, the distance in the second direction Y between the second modified portion 12 and the fifth modified portion 15 means the shortest distance in the second direction Y between the outer edge of the second modified portion 12 and the outer edge of the fifth modified portion 15.

[0046] The pulse energy of the laser light in the fifth step is preferably, for example, 4.3 μJ or more and 10.0 μJ or less, and more preferably 5.2 μJ or more and 9.2 μJ or less.

[0047] The irradiation interval of the laser light in the fifth step is preferably, for example, 6.0 μm to 17.0 μm, more preferably 7.0 μm to 16.0 μm, and even more preferably 8.0 μm to 15.0 μm.

[0048] According to this embodiment, as shown in Figures 12 and 13, in the first irradiation step, the second step of forming the second modified portion 12 and the fifth step of forming the fifth modified portion 15 are performed multiple times at different positions in the thickness direction Z of the sapphire substrate 10, moving from the first surface 10A to the second surface 10B.

[0049] For example, the second step is performed six times at different positions in the thickness direction Z of the sapphire substrate 10 to form six layers of second modified portions 12 that are spaced apart from each other in the thickness direction Z of the sapphire substrate 10. As shown in Figure 13, at each of the different positions in the thickness direction Z of the sapphire substrate 10, multiple second modified portions 12 are arranged in the first direction X. In the thickness direction Z of the sapphire substrate 10, the second modified portions 12 are formed in order from the one closest to the first surface 10A.

[0050] For example, the fifth step is performed three times at different positions in the thickness direction Z of the sapphire substrate 10 to form three layers of fifth modified portions 15 that are spaced apart from each other in the thickness direction Z of the sapphire substrate 10. At each of the different positions in the thickness direction Z of the sapphire substrate 10, multiple fifth modified portions 15 are arranged in the first direction X. In the thickness direction Z of the sapphire substrate 10, the fifth modified portions 15 are formed in order from the one closest to the first surface 10A.

[0051] According to this embodiment, after forming the third layer of the second modified section 12, including the first modified section 11, from the first surface 10A side, the first layer of the fifth modified section 15 is formed adjacent to the third layer of the second modified section 12 in the second direction Y, from the first surface 10A side. After forming the first layer of the fifth modified section 15 from the first surface 10A side, the fourth layer of the second modified section 12 is formed from the first surface 10A side. After forming the fourth layer of the second modified section 12 from the first surface 10A side, the second layer of the fifth modified section 15 is formed adjacent to the fourth layer of the second modified section 12 in the second direction Y, from the first surface 10A side. After forming the second layer of the fifth modified section 15 from the first surface 10A side, the fifth layer of the second modified section 12 is formed from the first surface 10A side. After forming the fifth layer of the second modified section 12 from the first surface 10A side, the third layer of the fifth modified section 15 is formed adjacent to the fifth layer of the second modified section 12 in the second direction Y from the first surface 10A side.

[0052] In this embodiment, the fifth modified portion 15 is not formed adjacent to the second modified portion 12 in the second direction Y of the second modified portion 12 from the first surface 10A side (the second modified portion 12 closest to the first surface 10A), the sixth modified portion 12 from the first surface 10A side, and the seventh modified portion 12 from the first surface 10A side (the second modified portion 12 closest to the second surface 10B).

[0053] By not forming a fifth modified portion 15 next to the second modified portion 12 closest to the second surface 10B, and instead forming a fifth modified portion 15 next to the second modified portion 12 other than the second modified portion 12 closest to the second surface 10B, it is possible to facilitate the propagation of cracks in the thickness direction Z of the sapphire substrate 10 while preventing the cracks from affecting the semiconductor layer 20.

[0054] The number of second modification sections 12 arranged in the thickness direction Z of the sapphire substrate 10 is greater than the number of fifth modification sections 15 arranged in the thickness direction Z of the sapphire substrate 10.

[0055] <Second irradiation process> The laser irradiation process further includes a second irradiation process in which, after the first irradiation process, laser light is irradiated along the second direction Y to form a plurality of modified regions within the sapphire substrate 10 along the second direction Y. In the second irradiation process, the laser light is irradiated along each of the plurality of dicing regions 100 extending in the second direction Y.

[0056] The second irradiation process will be described with reference to Figures 14 to 19. Figures 14 and 17 show XZ cross-sections perpendicular to the second direction Y. Figures 15 and 18 show YZ cross-sections parallel to the second direction Y. Figures 16 and 19 are plan views of the second surface 10B of the wafer W as seen from the positive direction of the Z axis.

[0057] (3rd step) The second irradiation step includes a third step of forming a plurality of third modified portions 13 along the second direction Y, as shown in Figures 14 to 16.

[0058] As shown in Figures 15 and 16, for example, adjacent third modified portions 13 in the second direction X are formed apart from each other in the second direction Y. Alternatively, parts of adjacent third modified portions 13 in the second direction Y may be in contact with or overlap each other.

[0059] Cracks extending from modified areas formed by irradiating the sapphire substrate 10 with laser light in the m-axis direction tend to be less elongated than cracks extending from modified areas formed by irradiating with laser light in the a-axis direction. Furthermore, when forming modified areas by irradiating with laser light in both the m-axis and a-axis directions, cracks may be less likely to extend in areas where the dicing regions 100 intersect and where the modified areas formed along the m-axis and the modified areas formed along the a-axis overlap. This is because, in areas where modified areas overlap, the laser light is irradiated onto areas where modified areas have already been formed, making it difficult to focus the laser light. When laser light is irradiated along the a-axis direction and then along the m-axis direction, modified areas have already been formed at the intersection of the dicing region 100 extending in the a-axis direction and the dicing region 100 extending in the m-axis direction due to the irradiation of the laser light along the a-axis direction. Because it is difficult to focus the laser light on the modified area, when forming the modified area by irradiating it with laser light in the m-axis direction, which is less prone to crack propagation than the a-axis direction, the crack becomes even less prone to propagation at the intersection mentioned above.

[0060] According to this embodiment, laser light is irradiated along a first direction X, which is along the m-axis, and then laser light is irradiated along a second direction Y, which is along the a-axis. This makes it easier for cracks to extend at the intersection of the dicing region 100 extending in the first direction X and the dicing region 100 extending in the second direction Y.

[0061] If laser light is irradiated along the first direction X and then along the second direction Y, it is difficult to form a modified portion at the intersection during the step of irradiating with laser light along the second direction Y. In this case, it is preferable that the amount of aberration correction of the laser light in the third step of forming a plurality of third modified portions 13 along the second direction Y is greater than the amount of aberration correction of the laser light in the first step of forming a plurality of first modified portions 11 along the first direction X. As a result, the focusing ability of the laser light in the third step, which is performed after the first step, is higher than in the first step, making it easier to form a modified portion at the intersection.

[0062] The pulse energy of the laser light in the third step is preferably, for example, 2.0 μJ or more and 10.3 μJ or less, more preferably 2.5 μJ or more and 9.5 μJ or less, and even more preferably 3.0 μJ or more and 8.9 μJ or less.

[0063] The irradiation interval of the laser light in the third step is preferably, for example, 6.0 μm to 18.0 μm, more preferably 7.0 μm to 17.0 μm, and even more preferably 8.0 μm to 16.0 μm.

[0064] (4th step) The second irradiation step further includes a fourth step, after the third step, in which a plurality of fourth modified portions 14 are formed along the second direction Y. As shown in Figures 17 to 19, in the fourth step, the fourth modified portion 14 is formed at a position closer to the second surface 10B than the third modified portion 13, and at a position that overlaps with the third modified portion 13 in a plan view. In a plan view, the third modified portion 13 and the fourth modified portion 14 overlap at least partially.

[0065] As shown in Figures 17 and 18, the fourth modified portion 14 is located between the third modified portion 13 and the second surface 10B in the thickness direction Z of the sapphire substrate 10. The third modified portion 13 is located between the fourth modified portion 14 and the first surface 10A in the thickness direction Z of the sapphire substrate 10, and is located closer to the semiconductor layer 20 than the fourth modified portion 14. In the thickness direction Z of the sapphire substrate 10, the fourth modified portion 14 is not in contact with the third modified portion 13. Cracks extending from the third modified portion 13 and cracks extending from the fourth modified portion 14 can be connected.

[0066] As shown in Figures 18 and 19, for example, adjacent fourth modified portions 14 in the second direction Y are formed apart from each other. Alternatively, parts of adjacent fourth modified portions 14 in the second direction Y may be in contact with or overlap each other.

[0067] As shown in Figures 17 and 18, the fourth step may be performed multiple times at different locations in the thickness direction Z of the sapphire substrate 10 to form multiple fourth modified portions 14 that are spaced apart from each other in the thickness direction Z of the sapphire substrate 10. The multiple fourth modified portions 14 are formed between the third modified portion 13 and the second surface 10B in the thickness direction Z of the sapphire substrate 10. The multiple fourth modified portions 14 do not touch each other in the thickness direction Z of the sapphire substrate 10. The multiple fourth modified portions 14 formed at different locations in the thickness direction Z of the sapphire substrate 10 overlap at least partially in a plan view. Cracks extending from each of the multiple fourth modified portions 14 can be connected to each other.

[0068] The pulse energy of the laser light in the fourth step is preferably, for example, 4.0 μJ or more and 10.3 μJ or less, more preferably 4.3 μJ or more and 9.5 μJ or less, and even more preferably 4.6 μJ or more and 8.9 μJ or less.

[0069] The irradiation interval of the laser light in the fourth step is preferably, for example, 6.0 μm to 18.0 μm, more preferably 7.0 μm to 17.0 μm, and even more preferably 8.0 μm to 16.0 μm.

[0070] (6th step) The second irradiation step may further include a sixth step in which a sixth modified portion 16 is formed adjacent to the fourth modified portion 14 in the first direction X, as shown in Figures 17 and 19. However, the sixth step is optional.

[0071] As shown in Figure 19, multiple sixth modified portions 16 are formed along a second direction Y adjacent to the fourth modified portion 14 in the first direction X. Adjacent sixth modified portions 16 in the second direction Y are formed apart from each other in the second direction Y. Alternatively, parts of adjacent sixth modified portions 16 in the second direction Y may be in contact with or overlap each other.

[0072] When a plurality of fourth modified portions 14 are formed in the thickness direction Z of the sapphire substrate 10, a sixth modified portion 16 is formed next to at least one of the plurality of fourth modified portions 14 in the thickness direction Z.

[0073] As shown in Figure 17, the fourth modified portion 14 and the sixth modified portion 16 are adjacent within the width of the dicing region 100. As shown in Figure 19, the third modified portion 13, the fourth modified portion 14, and the sixth modified portion 16 do not overlap the semiconductor layer 20 in a plan view.

[0074] The pulse energy of the laser light in the sixth step is preferably, for example, 4.0 μJ or more and 10.3 μJ or less, more preferably 4.3 μJ or more and 9.5 J or less, and even more preferably 4.6 μJ or more and 8.9 μJ or less.

[0075] The irradiation interval of the laser light in the sixth step is preferably, for example, 6.0 μm to 18.0 μm, more preferably 7.0 μm to 17.0 μm, and even more preferably 8.0 μm to 16.0 μm.

[0076] By forming a sixth modified section 16 next to the fourth modified section 14, the extension of cracks originating from the fourth modified section 14 can be accelerated. This makes it easier to cleave the sapphire substrate 10 in the subsequent cleavage process, even if the sapphire substrate 10 is relatively thick.

[0077] The distance in the first direction X between the adjacent fourth modified portion 14 and sixth modified portion 16 is preferably, for example, 2 μm or more and 10 μm or less. This makes it easier for the force released when the strain generated when forming the sixth modified portion 16 is released to act on the cracks extending from the already formed fourth modified portion 14. Here, the distance in the first direction X between the fourth modified portion 14 and the sixth modified portion 16 means the shortest distance in the first direction X between the outer edge of the fourth modified portion 14 and the outer edge of the sixth modified portion 16.

[0078] According to this embodiment, as shown in Figures 17 and 18, in the second irradiation step, the fourth step for forming the fourth modified portion 14 and the sixth step for forming the sixth modified portion 16 are performed multiple times at different positions in the thickness direction Z of the sapphire substrate 10, moving from the first surface 10A to the second surface 10B.

[0079] For example, the fourth step is performed six times at different positions in the thickness direction Z of the sapphire substrate 10 to form six layers of fourth modified portions 14 that are spaced apart from each other in the thickness direction Z of the sapphire substrate 10. As shown in Figure 18, at each of the different positions in the thickness direction Z of the sapphire substrate 10, multiple fourth modified portions 14 are arranged in the second direction Y. In the thickness direction Z of the sapphire substrate 10, the fourth modified portions 14 are formed in order from the one closest to the first surface 10A.

[0080] For example, the sixth step is performed three times at different positions in the thickness direction Z of the sapphire substrate 10 to form three layers of sixth modified portions 16 that are spaced apart from each other in the thickness direction Z of the sapphire substrate 10. At each of the different positions in the thickness direction Z of the sapphire substrate 10, multiple sixth modified portions 16 are arranged in the first direction X. In the thickness direction Z of the sapphire substrate 10, the sixth modified portions 16 are formed in order from the one closest to the first surface 10A.

[0081] According to this embodiment, after forming the third layer of the fourth modified section 14, including the third modified section 13, from the first surface 10A side, the first layer of the sixth modified section 16 is formed adjacent to the third layer of the fourth modified section 14 in the first direction X, from the first surface 10A side. After forming the first layer of the sixth modified section 16 from the first surface 10A side, the fourth layer of the fourth modified section 14 is formed from the first surface 10A side. After forming the fourth layer of the fourth modified section 14 from the first surface 10A side, the fifth layer of the fourth modified section 14 is formed from the first surface 10A side. After forming the fifth layer of the fourth modified section 14 from the first surface 10A side, the second layer of the sixth modified section 16 is formed adjacent to the fifth layer of the fourth modified section 14 in the first direction X, from the first surface 10A side. After forming the second layer of the sixth modified section 16 from the first surface 10A side, the sixth layer of the fourth modified section 14 is formed from the first surface 10A side. After forming the sixth layer of the fourth modified section 14 from the first surface 10A side, the seventh layer of the fourth modified section 14 (the fourth modified section 14 closest to the second surface 10B) is formed from the first surface 10A side. After forming the seventh layer of the fourth modified section 14 from the first surface 10A side, the third layer of the sixth modified section 16 is formed adjacent to the seventh layer of the fourth modified section 14 in the first direction X from the first surface 10A side.

[0082] A sixth modified portion 16 is not formed adjacent to the second fourth modified portion 14 from the first surface 10A side (the fourth modified portion 14 closest to the first surface 10A), the fourth fourth modified portion 14 from the first surface 10A side, and the sixth fourth modified portion 14 from the first surface 10A side, in the first direction X.

[0083] By not forming a sixth modified portion 16 next to the fourth modified portion 14 closest to the second surface 10B, and instead forming a sixth modified portion 16 next to the fourth modified portion 14 other than the fourth modified portion 14 closest to the second surface 10B, it is possible to facilitate the propagation of cracks in the thickness direction Z of the sapphire substrate 10 while preventing the cracks from affecting the semiconductor layer 20.

[0084] The number of the multiple fourth modification sections 14 aligned in the thickness direction Z of the sapphire substrate 10 is greater than the number of the multiple sixth modification sections 16 aligned in the thickness direction Z of the sapphire substrate 10.

[0085] As mentioned above, cracks do not extend as easily in the m-axis direction as in the a-axis direction. Therefore, in the first irradiation step, in which laser light is irradiated in the first direction X along the m-axis, it is preferable that the number of times the second and fifth steps are performed at different positions in the thickness direction Z of the sapphire substrate 10 is greater than the number of times the fourth and sixth steps are performed at different positions in the thickness direction Z of the sapphire substrate 10 in the second irradiation step, in which laser light is irradiated in the second direction Y along the a-axis. This makes it easier for cracks to extend in the m-axis direction.

[0086] As shown in Figure 12, in the first irradiation process, the second step of forming the second modified portion 12 and the fifth step of forming the fifth modified portion 15 are performed at different positions in the thickness direction Z of the sapphire substrate 10, thereby forming adjacent fifth modified portions 15 in the thickness direction Z of the sapphire substrate 10. In the example shown in Figure 12, three layers of fifth modified portions 15 are adjacent to each other in the thickness direction Z of the sapphire substrate 10.

[0087] The pair of the second modified portion 12 and the adjacent fifth modified portion 15 on the relatively lower layer side (closer to the first surface 10A) is designated as the first pair. After the first pair is formed, the pair of the second modified portion 12 and the adjacent fifth modified portion 15 formed adjacent to the first pair in the thickness direction Z of the sapphire substrate 10 is designated as the second pair. In the first irradiation process, immediately after the second and fifth steps that form the first pair, the second step that forms only the second modified portion 12 without forming a pair with the fifth modified portion 15 is omitted, and the second and fifth steps that form the second pair are performed instead.

[0088] When laser light is irradiated into a region with a high crack density, the laser light is difficult to focus, and less energy is used to form the modified region. As a result, more light escapes to the first surface 10A side, raising concerns about damage to the semiconductor layer 20. Since cracks do not extend as easily in the m-axis direction as in the a-axis direction, even if the first and second pairs are placed adjacent to each other in the thickness direction Z of the sapphire substrate 10, cracks do not easily extend to the region where the second pair is formed when the first pair is formed. Therefore, it is possible to reduce the increase in crack density in the region where the second pair is formed after the first pair has been formed, and to reduce the amount of light that escapes when laser light is irradiated to form the second pair.

[0089] Cracks extending from modified areas formed by irradiation with laser light in the a-axis direction tend to extend more easily than cracks extending from modified areas formed by irradiation with laser light in the m-axis direction. Therefore, as shown in Figure 17, it is preferable that in the second irradiation step, the pair of the fourth modified area 14 and its adjacent sixth modified area 16 are not adjacent in the thickness direction of the sapphire substrate 10. This reduces the amount of light loss during laser irradiation when forming the pair of the fourth modified area 14 and its adjacent sixth modified area 16, which are relatively on the upper layer side (closer to the second surface 10B).

[0090] [Separation process] After the laser irradiation process, the wafer W is separated into multiple semiconductor elements in the separation process. In the separation process, for example, the sapphire substrate 10 is pressed from the first surface 10A side with a pressing member to cut the sapphire substrate 10.

[0091] For example, the side of the wafer W on which the semiconductor layer 20 is located is bonded to a sheet, and the sapphire substrate 10 is pressed from the first surface 10A side through the sheet with a pressing member. The pressing member is, for example, a blade-shaped member that extends along the dicing region 100. The sapphire substrate 10, which receives the pressing force from the pressing member from the first surface 10A side, begins to crack starting from a crack that reaches or is near the second surface 10B from the modified portion. A V-shaped groove is formed along the dicing region 100 that opens to the second surface 10B, and this groove reaches the first surface 10A, causing the wafer W including the sapphire substrate 10 to cleave.

[0092] For example, first, the wafer W is cut along multiple dicing regions 100 extending in a first direction X, and the wafer W is separated into multiple bars 50 extending in the first direction X, as shown in Figure 20.

[0093] Next, the bar 50 is cut along multiple dicing regions 100 extending in the second direction Y, and the wafer W is divided into multiple semiconductor elements 1 as shown in Figure 21. Alternatively, the cutting along the second direction Y may be performed first, followed by the cutting along the first direction X.

[0094] On the side surfaces of each individual semiconductor element 1, the first modified portion 11, the second modified portion 12, the third modified portion 13, and the fourth modified portion 14 are exposed as regions with a greater surface roughness than the regions where no modified portion is formed. The fifth modified portion 15 and the sixth modified portion 16 are located inside the sapphire substrate 10.

[0095] For example, in the semiconductor element 1 of this embodiment, which is a light-emitting element, the light emitted from the active layer of the semiconductor layer 20 is extracted to the outside of the semiconductor element 1 from the second surface 10B and the side surface of the sapphire substrate 10. Furthermore, light is more easily extracted from the modified area exposed on the side surface of the sapphire substrate 10 than from the non-modified area on the side surface of the sapphire substrate 10. This is thought to be because the surface roughness of the modified area exposed on the side surface of the sapphire substrate 10 is greater than the surface roughness of the non-modified area on the side surface of the sapphire substrate 10, so light incident on the interior of the sapphire substrate 10 is more easily scattered in the modified area exposed on the side surface of the sapphire substrate 10.

[0096] By increasing the number of modified areas exposed on the side surface of the sapphire substrate 10, the area on the side surface of the sapphire substrate 10 from which light can be easily extracted can be increased. This improves the optical output of the semiconductor device 1.

[0097] Embodiments of this disclosure may include the following methods for manufacturing semiconductor devices.

[0098] [Section 1] A step of preparing a wafer having a sapphire substrate having a first surface and a second surface located opposite the first surface, and a semiconductor layer disposed on the first surface, A laser beam irradiation step in which laser light is irradiated into the interior of the sapphire substrate from the second surface side, Following the laser light irradiation step, a separation step is performed to separate the wafer into a plurality of semiconductor elements, Equipped with, The laser light irradiation step includes a first irradiation step of irradiating the sapphire substrate with the laser light along a first direction to form a plurality of modified portions along the first direction inside the sapphire substrate, The first irradiation step includes a first step of forming a plurality of first modified portions along the first direction, A second step is to form a plurality of second modified portions along the first direction at a position closer to the second surface than the first modified portion, and at a position that overlaps the first modified portion in a plan view, after the first step, It has, The amount of aberration correction for the laser light in the first step is smaller than the amount of aberration correction for the laser light in the second step. A method for manufacturing a semiconductor device, wherein the pulse energy of the laser light in the first step is smaller than the pulse energy of the laser light in the second step. [Section 2] The method for manufacturing a semiconductor device according to item 1, wherein the irradiation interval of the laser light along the first direction in the first step is smaller than the irradiation interval of the laser light along the first direction in the second step. [Section 3] The laser light irradiation step is, A method for manufacturing a semiconductor device according to claim 1 or 2, further comprising a second irradiation step of irradiating the sapphire substrate with the laser light along a second direction after the first irradiation step to form a plurality of modified portions along the second direction inside the sapphire substrate. [Section 4] The second irradiation step is, A third step involves forming a plurality of third modified portions along the second direction inside the sapphire substrate, A fourth step is to form a plurality of fourth modified portions along the second direction at a position closer to the second surface than the third modified portion, and at a position overlapping the third modified portion in a plan view, after the third step, It has, The amount of aberration correction for the laser light in the third step is greater than the amount of aberration correction for the laser light in the first step. The method for manufacturing a semiconductor device according to item 3, wherein the first direction is along the m-axis of the sapphire substrate, and the second direction is along the a-axis of the sapphire substrate. [Section 5] The first irradiation step includes a fifth step of forming a fifth modified portion adjacent to the second modified portion in the second direction, The method for manufacturing a semiconductor device according to claim 4, wherein the second irradiation step comprises a sixth step of forming a sixth modified portion adjacent to the fourth modified portion in the first direction. [Section 6] The method for manufacturing a semiconductor device according to item 5, wherein the number of times the second and fifth steps are performed at different locations in the thickness direction of the sapphire substrate in the first irradiation step is greater than the number of times the fourth and sixth steps are performed at different locations in the thickness direction of the sapphire substrate in the second irradiation step. [Section 7] In the first irradiation step, the second step and the fifth step are performed at different positions in the thickness direction of the sapphire substrate to form the fifth modified portion adjacent to each other in the thickness direction. A method for manufacturing a semiconductor device according to item 5 or 6, wherein in the second irradiation step, the fourth step and the sixth step are performed at different positions in the thickness direction of the sapphire substrate to form the sixth modified portion so that it is not adjacent in the thickness direction. [Section 8] A method for manufacturing a semiconductor device according to any one of items 1 to 7, wherein the thickness of the sapphire substrate is 400 μm or more and 1000 μm or less.

[0099] The embodiments of this disclosure have been described above with reference to specific examples. However, this disclosure is not limited to these specific examples. All forms that a person skilled in the art can implement by appropriately modifying the design based on the embodiments described above in this disclosure also fall within the scope of this disclosure, insofar as they encompass the gist of this disclosure. Furthermore, within the scope of the idea of ​​this disclosure, a person skilled in the art can conceive of various modifications and variations, and these modifications and variations also fall within the scope of this disclosure. [Explanation of symbols]

[0100] 1...Semiconductor element, 10...Sapphire substrate, 10A...First surface, 10B...Second surface, 11...First modified area, 12...Second modified area, 13...Third modified area, 14...Fourth modified area, 15...Fifth modified area, 16...Sixth modified area, 20...Semiconductor layer, 50...Bar, 90...Orientation flat, 100...Dicing area, W...Wafer

Claims

1. A step of preparing a wafer having a sapphire substrate having a first surface and a second surface located opposite to the first surface, and a semiconductor layer disposed on the first surface, A laser beam irradiation step in which laser light is irradiated into the interior of the sapphire substrate from the second side, Following the laser light irradiation step, a separation step is performed to separate the wafer into a plurality of semiconductor elements, Equipped with, The laser light irradiation step includes a first irradiation step of irradiating the sapphire substrate with the laser light along a first direction to form a plurality of modified portions along the first direction inside the sapphire substrate, The first irradiation step includes a first step of forming a plurality of first modified portions along the first direction, A second step is to form a plurality of second modified portions along the first direction at a position closer to the second surface than the first modified portion, and at a position that overlaps the first modified portion in a plan view, after the first step, It has, The amount of aberration correction for the laser light in the first step is smaller than the amount of aberration correction for the laser light in the second step. A method for manufacturing a semiconductor device, wherein the pulse energy of the laser light in the first step is smaller than the pulse energy of the laser light in the second step.

2. The method for manufacturing a semiconductor device according to claim 1, wherein the irradiation interval of the laser light along the first direction in the first step is smaller than the irradiation interval of the laser light along the first direction in the second step.

3. The laser light irradiation step is, A method for manufacturing a semiconductor device according to claim 1 or 2, further comprising a second irradiation step of irradiating the sapphire substrate with the laser light along a second direction after the first irradiation step to form a plurality of modified portions along the second direction inside the sapphire substrate.

4. The second irradiation step is, A third step involves forming a plurality of third modified portions along the second direction inside the sapphire substrate, A fourth step is to form a plurality of fourth modified portions along the second direction at a position closer to the second surface than the third modified portion, and at a position overlapping the third modified portion in a plan view, after the third step, It has, The amount of aberration correction for the laser light in the third step is greater than the amount of aberration correction for the laser light in the first step. The method for manufacturing a semiconductor element according to claim 3, wherein the first direction is along the m-axis of the sapphire substrate, and the second direction is along the a-axis of the sapphire substrate.

5. The first irradiation step includes a fifth step of forming a fifth modified portion adjacent to the second modified portion in the second direction, The method for manufacturing a semiconductor device according to claim 4, wherein the second irradiation step comprises a sixth step of forming a sixth modified portion adjacent to the fourth modified portion in the first direction.

6. The method for manufacturing a semiconductor device according to claim 5, wherein the number of times the second and fifth steps are performed at different locations in the thickness direction of the sapphire substrate in the first irradiation step is greater than the number of times the fourth and sixth steps are performed at different locations in the thickness direction of the sapphire substrate in the second irradiation step.

7. In the first irradiation step, the second step and the fifth step are performed at different positions in the thickness direction of the sapphire substrate to form the fifth modified portion adjacent to each other in the thickness direction. The method for manufacturing a semiconductor device according to claim 5, wherein in the second irradiation step, the fourth step and the sixth step are performed at different positions in the thickness direction of the sapphire substrate to form the sixth modified portion so that it is not adjacent in the thickness direction.

8. The method for manufacturing a semiconductor device according to claim 3, wherein the thickness of the sapphire substrate is 400 μm or more and 1000 μm or less.

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