Semiconductor device manufacturing method

Abstract

To provide a semiconductor device manufacturing method that can reduce the degradation of semiconductor device quality. [Solution] The laser light irradiation process comprises a first step, a second step, and a third step. The first step comprises forming a plurality of first modified portions in the substrate along a first direction. The second step comprises forming a plurality of second modified portions in the substrate along a second direction. The third step comprises forming a plurality of third modified portions in the substrate along a third direction. The laser light irradiation interval in the step of forming the third modified portions is greater than the laser light irradiation interval in the step of forming the first modified portions and the laser light irradiation interval in the step of forming the second modified portions.

Description

Technical Field

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

Background Art

[0002] For example, Patent Document 1 discloses a method for separating a wafer into a plurality of semiconductor devices having a hexagonal shape in a top view.

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 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 substrate with laser light from the second surface side; and a separation step after the laser light irradiation step of separating the wafer into a plurality of semiconductor devices having a hexagonal shape when viewed from above, wherein the laser light irradiation step comprises a first step of irradiating the laser light along a first direction to form a plurality of modified parts in the interior of the substrate along the first direction; and a second step after the first step of irradiating the laser light along a second direction to form a plurality of modified parts in the interior of the substrate along the second direction. The process comprises the first step of forming a plurality of first modified parts in the substrate along the first direction, the second step of forming a plurality of second modified parts in the substrate along the second direction, and the third step of forming a plurality of third modified parts in the substrate along the third direction, wherein the irradiation interval of the laser light in the step of forming the third modified parts is greater than the irradiation interval of the laser light in the step of forming the first modified parts and the irradiation interval of the laser light in the step of forming the second modified parts. [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 cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 2] This is a schematic top 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 top view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 5] This is a schematic cross-sectional view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Figure 6] This is a schematic top 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 top view illustrating one step in the manufacturing method of a semiconductor device according to the embodiment. [Modes for carrying out the invention]

[0008] The following description will explain a method for manufacturing a semiconductor device according to the embodiments of this disclosure, with reference to the drawings. The embodiments shown below are illustrative examples of a method for manufacturing a semiconductor device that embodies the technical concept of this embodiment, and are not limited to those described below. Furthermore, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments are merely illustrative examples and are not intended to limit the scope of this disclosure unless specifically stated otherwise. Note that the size, positional relationships, etc. of the components shown in each drawing may be exaggerated for clarity of explanation. In addition, in the following description, the same name and reference numeral indicate the same or identical components, and detailed explanations will be omitted as appropriate.

[0009] In the following description, terms indicating specific directions or positions (e.g., "up," "down," and other terms including these) may be used. However, these terms are used merely for clarity to indicate the relative directions or positions in the referenced drawings. If the relative directional or positional relationships expressed by terms such as "up" and "down" in the referenced drawings are the same, the arrangement in drawings other than those disclosed, actual products, etc., does not have to be the same as in the referenced drawings. In this specification, the positional relationship expressed as "up (or down)" includes, for example, the case where two members are in contact with each other, and the case where the two members are not in contact but one member is located above (or below) the other member.

[0010] The method for manufacturing a semiconductor element according to this embodiment comprises a step of preparing a wafer, a step of irradiating the wafer with laser light, and a separation step of separating the wafer into a plurality of semiconductor elements. Each step will be described below.

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

[0012] The wafer W has a substrate 10. The 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 substrate 10. The substrate 10 is, for example, a sapphire substrate. The thickness of the substrate 10 is, for example, 200 μm. The thickness range of the substrate 10 is, for example, 100 μm or more and 1000 μm or less.

[0013] 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 a sapphire substrate. The first surface 10A may be tilted with respect to the c-plane of the sapphire substrate to a degree that allows for the formation of the semiconductor layer 20 with good crystallinity.

[0014] 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 Ga1-x-y It includes a nitride semiconductor represented by N(0≦x≦1, 0≦y≦1, x + y≦1). The peak wavelength of the light emitted by the active layer of the semiconductor layer 20 is, for example, 200 nm or more and 600 nm or less.

[0015] On the first surface 10A side of the substrate 10, a conductive member electrically connected to the semiconductor layer 20, a protective film covering the semiconductor layer 20, etc. may be further arranged.

[0016] [Laser light irradiation process] In the laser light irradiation process, laser light is irradiated into the substrate 10 from the second surface 10B side. The laser light is condensed at a position where the distance from the second surface 10B inside the substrate 10 is a predetermined distance, and the energy of the laser light is concentrated at that position. A modified portion is formed in the region where the laser light is condensed inside the substrate 10. At least one of the density, refractive index, and mechanical strength in the modified portion is different from at least one of the density, refractive index, and mechanical strength in the unmodified region around the modified portion. A plurality of cracks can occur in a plurality of directions from one modified portion. Cracks branching from one crack can also occur.

[0017] The laser light is emitted, for example, in a pulsed manner. The pulse width of the laser light is, for example, 100 femtoseconds or more and 1000 picoseconds or less. As the laser light source, for example, a Nd:YAG laser, a titanium sapphire laser, a Nd:YVO4 laser, or a Nd:YLF laser, etc. is used. The wavelength of the laser light is the wavelength of the light that transmits through the substrate 10. The laser light has a peak wavelength, for example, in the range of 500 nm or more and 1200 nm or less.

[0018] <First step> The laser irradiation process includes a first step. The first step will be described with reference to Figures 2 and 3. Figure 2 is a top view of the second surface 10B of the wafer W viewed from the positive Z-axis direction. In Figures 2 and 3, the first direction d1 is shown. The first direction d1 is perpendicular to the thickness direction Z of the substrate 10. In this embodiment, the first direction d1 is, for example, the direction along the m-axis of the sapphire substrate. Figure 3 is a cross-sectional view of the wafer W parallel to the first direction d1 and the thickness direction Z of the substrate 10.

[0019] As shown in Figure 2, in the first step, laser light is irradiated along the first direction d1 to form a plurality of modified portions 100 inside the substrate 10 along the first direction d1. The plurality of modified portions 100 formed along the first direction d1 in the first step include the first modified portion 11, the fourth modified portion 14, and the fifth modified portion 15, which will be described later. The first modified portion 11, the fourth modified portion 14, and the fifth modified portion 15 are formed at different positions in the thickness direction Z of the substrate 10.

[0020] The multiple modified portions 100 formed along the first direction d1 in the first step are formed in the regions between multiple semiconductor elements that are separated into individual pieces by the cutting of the substrate 10, which will be described later.

[0021] Figure 3 is a cross-sectional view of a region between semiconductor elements where the first modified portion 11, the fourth modified portion 14, and the fifth modified portion 15 are formed along the first direction d1. As shown in Figure 3, the first step includes forming a plurality of first modified portions 11 inside the substrate 10 along the first direction d1. For example, parts of adjacent first modified portions 11 in the first direction d1 may be in contact with or overlap each other. Adjacent first modified portions 11 in the first direction d1 may be formed apart from each other in the first direction d1.

[0022] In the process of forming the first modified portion 11, the first modified portion 11 is formed along the first direction d1 at a first position at a first distance from the second surface 10B. The first distance is, for example, 60 μm or more and 90 μm or less. At least a portion of the first modified portion 11 is located at the first position in the thickness direction Z of the substrate 10.

[0023] <Second process> The laser irradiation process includes a second step after the first step. The second step will be described with reference to Figures 4 and 5. Figure 4 is a top view of the second surface 10B of the wafer W viewed from the positive Z-axis direction. In Figures 4 and 5, the second direction d2 is shown. The second direction d2 is perpendicular to the thickness direction Z of the substrate 10. In this embodiment, the second direction d2 is, for example, the direction along the m-axis of the sapphire substrate. Figure 5 is a cross-sectional view of the wafer W parallel to the second direction d2 and the thickness direction Z of the substrate 10.

[0024] As shown in Figure 4, in the second step, laser light is irradiated along the second direction d2 to form a plurality of modified portions 200 inside the substrate 10 along the second direction d2. The plurality of modified portions 200 formed along the second direction d2 in the second step include the second modified portion 12, the sixth modified portion 16, and the seventh modified portion 17, which will be described later. The second modified portion 12, the sixth modified portion 16, and the seventh modified portion 17 are formed at different positions in the thickness direction Z of the substrate 10. A first row containing a plurality of modified portions 100 arranged along the first direction d1 and a second row containing a plurality of modified portions 200 arranged along the second direction d2 are connected at a predetermined angle when viewed from above. The smaller of the angles formed between the first row and the second row at the point where the first row and the second row connect is approximately 60°.

[0025] In the second step, the multiple modified portions 200 formed along the second direction d2 are formed in the regions between multiple semiconductor elements that are separated into individual pieces by the cutting of the substrate 10, as described later.

[0026] Figure 5 is a cross-sectional view of the region between semiconductor elements where the second modified portion 12, the sixth modified portion 16, and the seventh modified portion 17 are formed along the second direction d2. As shown in Figure 5, the second step includes forming a plurality of second modified portions 12 inside the substrate 10 along the second direction d2. For example, parts of adjacent second modified portions 12 in the second direction d2 may be in contact with or overlap each other. Adjacent second modified portions 12 in the second direction d2 may be formed apart from each other in the second direction d2.

[0027] In the process of forming the second modified portion 12, the second modified portion 12 is formed along the second direction d2 at a first position at a first distance from the second surface 10B. At least a portion of the second modified portion 12 is located at the first position in the thickness direction Z of the substrate 10.

[0028] <3rd process> The laser irradiation process includes a third step after the second step. The third step will be described with reference to Figures 6 and 7. Figure 6 is a top view of the second surface 10B of the wafer W viewed from the positive Z-axis direction. In Figures 6 and 7, the third direction d3 is shown. The third direction d3 is perpendicular to the thickness direction Z of the substrate 10. In this embodiment, the third direction d3 is, for example, the direction along the m-axis of the sapphire substrate. Figure 7 is a cross-sectional view of the wafer W parallel to the third direction d3 and the thickness direction Z of the substrate 10.

[0029] As shown in Figure 6, in the third step, laser light is irradiated along the third direction d3 to form a plurality of modified portions 300 inside the substrate 10 along the third direction d3. The plurality of modified portions 300 formed along the third direction d3 in the third step include the third modified portion 13, the eighth modified portion 18, and the ninth modified portion 19, which will be described later. The third modified portion 13, the eighth modified portion 18, and the ninth modified portion 19 are formed at different positions in the thickness direction Z of the substrate 10. The first row, which includes a plurality of modified portions 100 arranged along the first direction d1, and the third row, which includes a plurality of modified portions 300 arranged along the third direction d3, are connected at a predetermined angle when viewed from above. The smaller of the angles formed between the first row and the third row at the point where the first row and the third row are connected is approximately 60°. Furthermore, the second and third rows, each containing multiple modified sections 200 aligned along the second direction d2, are connected at a predetermined angle when viewed from above. The smaller of the angles formed between the second and third rows at the point where they connect is approximately 60°.

[0030] In the third step, the multiple modified portions 300 formed along the third direction d3 are formed in the regions between multiple semiconductor elements that are separated into individual pieces by the cutting of the substrate 10, as described later. According to this embodiment, the multiple modified portions 100 formed along the first direction d1, the multiple modified portions 200 formed along the second direction d2, and the multiple modified portions 300 formed along the third direction d3 form the sides of multiple hexagons adjacent to each other in a top view.

[0031] Figure 7 is a cross-sectional view of the region between semiconductor elements where the third modified portion 13, the eighth modified portion 18, and the ninth modified portion 19 are formed along the third direction d3. As shown in Figure 7, the third step includes forming a plurality of third modified portions 13 along the third direction d3 inside the substrate 10. For example, adjacent third modified portions 13 in the third direction d3 are formed apart from each other in the third direction d3. Alternatively, parts of adjacent third modified portions 13 in the third direction d3 may be in contact with each other or overlap.

[0032] In the process of forming the third modified portion 13, the third modified portion 13 is formed along the third direction d3 at a first position at a first distance from the second surface 10B. At least a portion of the third modified portion 13 is located at the first position in the thickness direction Z of the substrate 10.

[0033] According to this embodiment, the irradiation interval along the third direction d3 of the laser beam in the step of forming the third modified portion 13 in the third step is greater than the irradiation interval along the first direction d1 of the laser beam in the step of forming the first modified portion 11 in the first step, and greater than the irradiation interval along the second direction d2 of the laser beam in the step of forming the second modified portion 12 in the second step.

[0034] In the process of forming the first modified portion 11, the irradiation interval along the first direction d1 of the laser beam is, for example, 1.0 μm or more and 3.0 μm or less. In the process of forming the second modified portion 12, the irradiation interval along the second direction d2 of the laser beam is, for example, 1.0 μm or more and 3.0 μm or less. In the process of forming the third modified portion 13, the irradiation interval along the third direction d3 of the laser beam is, for example, 3.0 μm or more and 6.0 μm or less.

[0035] After a modified portion is formed inside the substrate 10, cracks extending from the modified portion are formed inside the substrate 10. The modified portion has higher mechanical strength than the area in the substrate 10 where the cracks are formed. Therefore, although the substrate 10 is prone to cracking due to the cracks extending from the modified portion, the substrate 10 does not crack and maintains its wafer state due to the multiple modified portions. Accordingly, by reducing the irradiation interval of the laser beam, the area of ​​the modified portion in the cross-section of the area to be fractured in the substrate 10 increases, and the fracture strength of the substrate 10 can be increased. As a result, unintended cracking of the substrate 10 before the separation process can be reduced. In addition, voids may be formed inside the modified portion. These voids inside the modified portion reduce the area of ​​the modified portion in the cross-section of the area to be fractured in the substrate 10, and thus reduce the fracture strength of the substrate 10. By reducing the irradiation interval of the laser beam to the extent that the voids inside the previously formed modified portion are filled by the modified portion formed immediately afterward, the voids inside the modified portion can be reduced. This further increases the area of ​​the modified portion in the cross-section of the planned fracture region of the substrate 10, thereby increasing the fracture strength of the substrate 10.

[0036] According to this embodiment, by making the laser irradiation interval in the process of forming the first modified portion 11 and the second modified portion 12 shorter than the laser irradiation interval in the process of forming the third modified portion 13, the area of ​​the first modified portion 11 and the second modified portion 12 in the cross-section of the planned fracture region of the substrate 10 can be increased, thereby increasing the fracture strength of the substrate 10.

[0037] If the laser irradiation interval in the process of forming the third modified section 13 is made to be the same as, or smaller than, the laser irradiation interval in the process of forming the first modified section 11 and the laser irradiation interval in the process of forming the second modified section 12, the cracks extending from the third modified section 13 tend to meander. The meandering of cracks extending from the third modified section 13 means that among the cracks extending from adjacent third modified sections 13 in the third direction d3, the cracks extending in a direction different from the third direction d3 in the top view connect with each other, causing the cracks to meander in the top view.

[0038] It is believed that the stress distribution inside the substrate 10 changed due to the first modified section 11, the second modified section 12, and the cracks extending from them, which were already formed before the process of forming the third modified section 13, and that this is the reason why the cracks extending from the third modified section 13 tend to meander during the third process.

[0039] According to this embodiment, by making the laser irradiation interval in the process of forming the third modified portion 13 larger than the laser irradiation interval in the process of forming the first modified portion 11 and the laser irradiation interval in the process of forming the second modified portion 12, the meandering of cracks extending from the third modified portion 13 can be reduced. More specifically, by increasing the laser irradiation interval in the process of forming the third modified portion 13, cracks extending from adjacent third modified portions 13 in the third direction d3 become more likely to connect when viewed from above in the third direction d3. By reducing the meandering of cracks, the influence of cracks on the semiconductor layer 20 can be reduced, and the shape of the semiconductor layer 20 can be stabilized.

[0040] As mentioned above, reducing the irradiation interval of the laser beam so that the voids inside the previously formed modified section are filled by the immediately formed modified section can reduce the voids inside the modified section. However, if the laser beam is irradiated to a location where a modified section has already been formed, changes in internal stress due to the newly formed modified section become less likely, and cracks are less likely to propagate. Therefore, if the pulse energy of the laser beam in the process of forming the first modified section 11 and the pulse energy of the laser beam in the process of forming the second modified section 12 are made to be about the same as or less than the pulse energy of the laser beam in the process of forming the third modified section 13, cracks from the first modified section 11 and cracks extending from the second modified section 12 will be less likely to propagate than cracks extending from the third modified section 13.

[0041] Therefore, it is preferable that the pulse energy of the laser light in the process of forming the first modified portion 11 is greater than the pulse energy of the laser light in the process of forming the third modified portion 13. By increasing the pulse energy of the laser light in the process of forming the first modified portion 11, cracks from the first modified portion 11 can be made to extend more easily. This makes it easier to cleave the substrate 10, as described later.

[0042] The pulse energy of the laser light in the step of forming the first modified portion 11 is, for example, 1.4 μJ or more and 2.2 μJ or less. The pulse energy of the laser light in the step of forming the third modified portion 13 is, for example, 1.2 μJ or more and 2.0 μJ or less.

[0043] Similarly, it is preferable that the pulse energy of the laser light in the process of forming the second modified portion 12 is greater than the pulse energy of the laser light in the process of forming the third modified portion 13. By increasing the pulse energy of the laser light in the process of forming the second modified portion 12, cracks from the second modified portion 12 can be made to extend more easily, making it easier to fracture the substrate 10. The pulse energy of the laser light in the process of forming the second modified portion 12 is, for example, the same as the pulse energy of the laser light in the process of forming the first modified portion 11. Alternatively, the pulse energy of the laser light in the process of forming the second modified portion 12 only needs to be greater than the pulse energy of the laser light in the process of forming the third modified portion 13, and does not need to be the same as the pulse energy of the laser light in the process of forming the first modified portion 11.

[0044] During irradiation with laser light to form a modified portion, aberrations may occur at the focal point of the laser light within the substrate 10 due to the refractive index difference between the air and the second surface 10B of the substrate 10. Aberrations are a phenomenon in which the light rays constituting the laser light do not converge to a single point but instead scatter. These aberrations can be corrected with a spatial light 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.

[0045] The ideal focusing state is defined as the state in which aberrations are reduced to the point where they approach the focusing state assuming there is no medium (sapphire substrate) by correcting for spherical aberration that occurs at the focal point 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 is performed to cancel out spherical aberration 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.

[0046] If the aberration correction amount is small, the focusing ability of the laser beam deteriorates, so the length of the modified portion of the substrate 10 in the thickness direction Z becomes longer than the length of the modified portion of the substrate 10 in the thickness direction Z formed with an ideal aberration correction amount. The length of the modified portion of the substrate 10 in the thickness direction Z represents the maximum length of the substrate 10 in the thickness direction Z.

[0047] Furthermore, if the aberration correction amount is small, 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. Also, if the pulse energy of the laser light is large, the damage to the semiconductor layer 20 caused by light that passes through to the first surface 10A side will be greater.

[0048] Therefore, when the pulse energy of the laser light used in the process of forming the first modified portion 11 is greater than the pulse energy of the laser light used in the process of forming the third modified portion 13, it is preferable that the length of the third modified portion 13 in the thickness direction Z of the substrate 10 is longer than the length of the first modified portion 11 in the thickness direction Z of the substrate 10.

[0049] As described above, for example, by making the aberration correction amount of the laser light in the process of forming the first modified portion 11 greater than the aberration correction amount of the laser light in the process of forming the third modified portion 13, the length of the third modified portion 13 in the thickness direction Z of the substrate 10 can be made longer than the length of the first modified portion 11 in the thickness direction Z of the substrate 10. This makes it possible to reduce the amount of light that passes through to the first surface 10A side in the process of forming the first modified portion 11 with a pulse energy greater than the pulse energy of the laser light in the process of forming the third modified portion 13, thereby reducing damage to the semiconductor layer 20. For example, the aberration correction amount of the laser light in the process of forming the first modified portion 11 is the ideal aberration correction amount, and the aberration correction amount of the laser light in the process of forming the third modified portion 13 is the weak aberration correction amount.

[0050] Similarly, it is preferable that the length of the third modified portion 13 in the thickness direction Z of the substrate 10 is longer than the length of the second modified portion 12 in the thickness direction Z of the substrate 10. This reduces the amount of light passing through to the first surface 10A side in the process of forming the second modified portion 12 with a pulse energy greater than the pulse energy of the laser light in the process of forming the third modified portion 13, thereby reducing damage to the semiconductor layer 20.

[0051] By making the amount of laser beam aberration correction in the process of forming the third modified section 13 smaller than the amount of laser beam aberration correction in the process of forming the first modified section 11, the length of the third modified section 13 in the thickness direction Z of the substrate 10 can be made longer than the length of the first modified section 11 in the thickness direction Z of the substrate 10. When the amount of laser beam aberration correction is small, the area that is focused by the pulse energy of the laser beam required to form the modified section becomes smaller, making it more difficult for cracks to extend. As a result, among the cracks extending from the third modified section 13 in multiple directions, it becomes less likely for cracks to connect in directions other than the third direction d3, and the meandering of cracks extending from the third modified section 13 can be reduced.

[0052] As shown in Figure 3, the first step may include a step of forming a plurality of fourth modified parts 14 along the first direction d1 at a second position at a second distance greater than the first distance from the second surface 10B, before the step of forming the first modified part 11, and a step of forming a plurality of fifth modified parts 15 along the first direction d1 at a third position at a third distance less than the first distance from the second surface 10B, after the step of forming the first modified part 11.

[0053] The second distance is, for example, 90 μm to 130 μm. At least a portion of the fourth modified portion 14 is located at the second position in the thickness direction Z of the substrate 10. The second position is closer to the first surface 10A than the first position where the first modified portion 11 is located. In a top view, at least a portion of the first modified portion 11 and the fourth modified portion 14 overlap.

[0054] In the thickness direction Z of the substrate 10, the first modified portion 11 is located away from the fourth modified portion 14. A crack extending from the fourth modified portion 14 and a crack extending from the first modified portion 11 can be connected.

[0055] For example, adjacent fourth modified portions 14 in the first direction d1 are formed separately from each other in the first direction d1. Alternatively, parts of adjacent fourth modified portions 14 in the first direction d1 may be in contact with or overlap each other.

[0056] The third distance is, for example, 20 μm or more and 50 μm or less. At least a portion of the fifth modified portion 15 is located at the third position in the thickness direction Z of the substrate 10. The third position is closer to the second surface 10B than the first position where the first modified portion 11 is located. In a top view, at least a portion of the fifth modified portion 15 and the first modified portion 11 overlap.

[0057] In the thickness direction Z of the substrate 10, the fifth modified portion 15 is located away from the first modified portion 11. Cracks extending from the first modified portion 11 and cracks extending from the fifth modified portion 15 can be connected.

[0058] For example, adjacent fifth modified portions 15 in the first direction d1 are formed separately from each other in the first direction d1. Alternatively, parts of adjacent fifth modified portions 15 in the first direction d1 may be in contact with or overlap each other.

[0059] By forming multiple modified portions along the first direction d1 at different positions in the thickness direction Z of the substrate 10, the area of ​​the modified portions in the cross-section of the planned cleavage region along the first direction d1 of the substrate 10 increases, thereby increasing the fracture strength of the substrate 10.

[0060] The laser irradiation interval in the process of forming the first modified portion 11 is smaller than the laser irradiation interval in the process of forming the fourth modified portion 14 and the laser irradiation interval in the process of forming the fifth modified portion 15.

[0061] As mentioned above, reducing the irradiation interval of the laser beam can reduce the voids inside the modified portion and increase the fracture strength of the substrate 10. Reducing the irradiation interval of the laser beam in the process of forming the fourth modified portion 14, which is closer to the first surface 10A than the first modified portion 11 and the fifth modified portion 15, makes it more difficult for cracks to extend from the fourth modified portion 14 toward the first surface 10A, and can make it more difficult to fracture the substrate 10. Reducing the irradiation interval of the laser beam in the process of forming the fifth modified portion 15, which is closer to the second surface 10B than the first modified portion 11 and the fourth modified portion 14, makes it more likely for cracks extending from the fifth modified portion 15 toward the second surface 10B to meander, and makes it more likely for chipping to occur on the second surface 10B side of the substrate 10. Chipping of the substrate 10 can lead to a decrease in the quality of the semiconductor device, such as variations in the shape of the semiconductor device.

[0062] Therefore, in this embodiment, it is preferable to increase the fracture strength of the substrate 10 by making the laser irradiation interval in the process of forming the first modified portion 11 smaller than the laser irradiation interval in the process of forming the fourth modified portion 14 and the laser irradiation interval in the process of forming the fifth modified portion 15.

[0063] Furthermore, it is preferable that the laser irradiation interval in the process of forming the fourth modified portion 14 is smaller than the laser irradiation interval in the process of forming the fifth modified portion 15. This makes it difficult for cracks to extend from the fourth modified portion 14 toward the first surface 10A, thereby reducing the impact of cracks on the semiconductor layer 20.

[0064] As mentioned above, the laser irradiation interval in the step of forming the first modified portion 11 is, for example, 1.0 μm or more and 3.0 μm or less. The laser irradiation interval in the step of forming the fourth modified portion 14 is, for example, 2.0 μm or more and 4.0 μm or less. The laser irradiation interval in the step of forming the fifth modified portion 15 is, for example, 4.0 μm or more and 7.0 μm or less.

[0065] By reducing the irradiation interval of the laser beam and irradiating the already formed modified portion or its vicinity with the laser beam, changes in internal stress due to the newly formed modified portion become less likely, and cracks are less likely to propagate. For this reason, it is preferable that the pulse energy of the laser beam in the step of forming the first modified portion 11, which has a shorter irradiation interval than the steps of forming the fourth modified portion 14 and the fifth modified portion 15, be greater than the pulse energy of the laser beam in the step of forming the fourth modified portion 14 and the pulse energy of the laser beam in the step of forming the fifth modified portion 15. This makes it easier for cracks from the first modified portion 11 to propagate, and makes it easier to fracture the substrate 10.

[0066] The fifth modified portion 15 is closer to the second surface 10B in the thickness direction Z of the substrate 10 than the fourth modified portion 14, and cracks extending from the fifth modified portion 15 are more likely to reach the second surface 10B. Therefore, the pulse energy of the laser light in the process of forming the fifth modified portion 15 can be made smaller than the pulse energy of the laser light in the process of forming the fourth modified portion 14. By making the pulse energy of the laser light in the process of forming the fifth modified portion 15 smaller, the amount of light passing through to the first surface 10A side in the process of forming the fifth modified portion 15 can be reduced, and damage to the semiconductor layer 20 can be reduced. In other words, it is preferable that the pulse energy of the laser light in the process of forming the fourth modified portion 14 is larger than the pulse energy of the laser light in the process of forming the fifth modified portion 15.

[0067] As mentioned above, the pulse energy of the laser light in the step of forming the first modified portion 11 is, for example, 1.4 μJ or more and 2.2 μJ or less. The pulse energy of the laser light in the step of forming the fourth modified portion 14 is, for example, 1.2 μJ or more and 2.0 μJ or less. The pulse energy of the laser light in the step of forming the fifth modified portion 15 is, for example, 1.0 μJ or more and 1.8 μJ or less.

[0068] As shown in Figure 5, the second step includes forming a plurality of sixth modified portions 16 along the second direction d2 at a second position at a second distance greater than the first distance from the second surface 10B, before forming the second modified portion 12, and forming a plurality of seventh modified portions 17 along the second direction d2 at a third position at a third distance less than the first distance from the second surface 10B, after forming the second modified portion 12.

[0069] In the thickness direction Z of the substrate 10, at least a portion of the sixth modified portion 16 is located at the second position. In the thickness direction Z of the substrate 10, the sixth modified portion 16 is located closer to the first surface 10A than the second modified portion 12. In a top view, at least a portion of the second modified portion 12 and the sixth modified portion 16 overlap.

[0070] In the thickness direction Z of the substrate 10, the second modified portion 12 is located away from the sixth modified portion 16. Cracks extending from the sixth modified portion 16 and cracks extending from the second modified portion 12 can be connected.

[0071] For example, adjacent sixth modified portions 16 in the second direction d2 are formed separately from each other in the second direction d2. Alternatively, parts of adjacent sixth modified portions 16 in the second direction d2 may be in contact with or overlap each other.

[0072] In the thickness direction Z of the substrate 10, at least a portion of the seventh modified portion 17 is located at the third position. In the thickness direction Z of the substrate 10, the seventh modified portion 17 is located closer to the second surface 10B than the second modified portion 12. In a top view, at least a portion of the seventh modified portion 17 and the second modified portion 12 overlap.

[0073] In the thickness direction Z of the substrate 10, the seventh modified portion 17 is located away from the second modified portion 12. A crack extending from the second modified portion 12 and a crack extending from the seventh modified portion 17 can be connected.

[0074] For example, adjacent seventh modified portions 17 in the second direction d2 are formed separately from each other in the second direction d2. Alternatively, parts of adjacent seventh modified portions 17 in the second direction d2 may be in contact with or overlap each other.

[0075] By forming multiple modified portions along the second direction d2 at different positions in the thickness direction Z of the substrate 10, the area of ​​the modified portions in the cross-section of the planned cleavage region along the second direction d2 of the substrate 10 increases, thereby increasing the fracture strength of the substrate 10.

[0076] The laser irradiation interval in the process of forming the second modified portion 12 is smaller than the laser irradiation interval in the process of forming the sixth modified portion 16 and the laser irradiation interval in the process of forming the seventh modified portion 17. This makes it possible to increase the fracture strength of the substrate 10. In addition, it is possible to extend the crack appropriately from the sixth modified portion 16 toward the first surface 10A. Furthermore, it is possible to reduce the meandering of the crack extending from the seventh modified portion 17 toward the second surface 10B.

[0077] Furthermore, it is preferable that the laser irradiation interval in the process of forming the sixth modified portion 16 is smaller than the laser irradiation interval in the process of forming the seventh modified portion 17. This reduces the impact on the semiconductor layer 20 due to cracks extending from the sixth modified portion 16.

[0078] The laser irradiation interval in the process of forming the second modified portion 12 is, for example, the same as the laser irradiation interval in the process of forming the first modified portion 11. The laser irradiation interval in the process of forming the sixth modified portion 16 is, for example, the same as the laser irradiation interval in the process of forming the fourth modified portion 14. The laser irradiation interval in the process of forming the seventh modified portion 17 is, for example, the same as the laser irradiation interval in the process of forming the fifth modified portion 15.

[0079] Furthermore, it is preferable that the pulse energy of the laser light in the step of forming the second modified portion 12, which has a shorter irradiation interval than the step of forming the sixth modified portion 16 and the step of forming the seventh modified portion 17, be greater than the pulse energy of the laser light in the step of forming the sixth modified portion 16 and the pulse energy of the laser light in the step of forming the seventh modified portion 17. This makes it easier for cracks from the second modified portion 12 to extend, and makes it easier to cleave the substrate 10.

[0080] Furthermore, similar to the relationship between the pulse energy of the laser light in the process of forming the fourth modified section 14 and the pulse energy of the laser light in the process of forming the fifth modified section 15, it is preferable that the pulse energy of the laser light in the process of forming the sixth modified section 16 is greater than the pulse energy of the laser light in the process of forming the seventh modified section 17.

[0081] The pulse energy of the laser light in the process of forming the second modified section 12 is, for example, the same as the pulse energy of the laser light in the process of forming the first modified section 11. The pulse energy of the laser light in the process of forming the sixth modified section 16 is, for example, the same as the pulse energy of the laser light in the process of forming the fourth modified section 14. The pulse energy of the laser light in the process of forming the seventh modified section 17 is, for example, the same as the pulse energy of the laser light in the process of forming the fifth modified section 15.

[0082] As shown in Figure 7, the third step includes the step of forming a plurality of eighth modified parts 18 along the third direction d3 at a second position at a second distance greater than the first distance from the second surface 10B, before the step of forming the third modified part 13, and the step of forming a plurality of ninth modified parts 19 along the third direction d3 at a third position at a third distance less than the first distance from the second surface 10B, after the step of forming the third modified part 13.

[0083] In the thickness direction Z of the substrate 10, at least a portion of the eighth modified portion 18 is located at the second position. In the thickness direction Z of the substrate 10, the eighth modified portion 18 is located closer to the first surface 10A than the third modified portion 13. In a top view, at least a portion of the third modified portion 13 and the eighth modified portion 18 overlap.

[0084] In the thickness direction Z of the substrate 10, the third modified portion 13 is located away from the eighth modified portion 18. A crack extending from the eighth modified portion 18 and a crack extending from the third modified portion 13 can be connected.

[0085] For example, adjacent eighth modified portions 18 in the third direction d3 are formed separately from each other in the third direction d3. Alternatively, parts of adjacent eighth modified portions 18 in the third direction d3 may be in contact with or overlap each other.

[0086] In the thickness direction Z of the substrate 10, at least a portion of the ninth modified portion 19 is located at the third position. In the thickness direction Z of the substrate 10, the ninth modified portion 19 is located closer to the second surface 10B than the third modified portion 13. In a top view, at least a portion of the ninth modified portion 19 and the third modified portion 13 overlap.

[0087] In the thickness direction Z of the substrate 10, the ninth modified portion 19 is located away from the third modified portion 13. A crack extending from the third modified portion 13 and a crack extending from the ninth modified portion 19 can be connected.

[0088] For example, adjacent ninth modified portions 19 in the third direction d3 are formed separately from each other in the third direction d3. Alternatively, parts of adjacent ninth modified portions 19 in the third direction d3 may be in contact with or overlap each other.

[0089] By forming multiple modified portions along the third direction d3 at different positions in the thickness direction Z of the substrate 10, the area of ​​the modified portions in the cross-section of the planned cleavage region along the third direction d3 of the substrate 10 increases, thereby increasing the fracture strength of the substrate 10.

[0090] The laser irradiation interval in the process of forming the eighth modified section 18 is smaller than the laser irradiation interval in the process of forming the third modified section 13 and the laser irradiation interval in the process of forming the ninth modified section 19. The laser irradiation interval in the process of forming the third modified section 13 is smaller than the laser irradiation interval in the process of forming the ninth modified section 19.

[0091] The irradiation interval of the laser beam in the step of forming the eighth modified portion 18 is, for example, 2.0 μm or more and 5.0 μm or less. The irradiation interval of the laser beam in the step of forming the third modified portion 13 is, for example, 3.0 μm or more and 6.0 μm or less. The irradiation interval of the laser beam in the step of forming the ninth modified portion 19 is, for example, 4.0 μm or more and 7.0 μm or less.

[0092] The pulse energy of the laser light in the step of forming the third modified section 13, the pulse energy of the laser light in the step of forming the eighth modified section 18, and the pulse energy of the laser light in the step of forming the ninth modified section 19 are, for example, the same.

[0093] [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 substrate 10 is pressed with a pressing member from the first surface 10A side via a stretchable sheet to cleave the substrate 10. The 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 in cross-section opening to the second surface 10B is formed along the direction in which the multiple modified portions are formed in a row, and this groove reaches the first surface 10A, cleaving the wafer W including the substrate 10. In the separation process, the wafer W may be placed on a stretchable sheet, and the substrate 10 may be pressed by applying air pressure from the side of the stretchable sheet where the wafer W is not placed.

[0094] Through the separation process, as shown in Figure 8, the wafer W is fragmented into multiple semiconductor elements 1, each having a hexagonal shape when viewed from above. For example, each semiconductor element 1 has a regular hexagonal shape when viewed from above. For example, the length of one side of each semiconductor element 1 is between 50 μm and 1500 μm.

[0095] On the side surfaces of the substrate 10 of each individual semiconductor element 1 that has been separated into individual pieces, the modified portions are exposed as regions with a greater surface roughness than the regions where no modified portions are formed. On the side surfaces cut along the first direction d1, the first modified portion 11, the fourth modified portion 14, and the fifth modified portion 15 are exposed. On the side surfaces cut along the second direction d2, the second modified portion 12, the sixth modified portion 16, and the seventh modified portion 17 are exposed. On the side surfaces cut along the third direction d3, the third modified portion 13, the eighth modified portion 18, and the ninth modified portion 19 are exposed. For example, on the side surfaces of the substrate 10, the multiple third modified portions 13 are formed more sparsely than the multiple first modified portions 11 and the multiple second modified portions 12.

[0096] Embodiments of this disclosure may include the following methods for manufacturing semiconductor devices.

[0097] [Section 1] A step of preparing a wafer having a 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 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 having a hexagonal shape when viewed from above, Equipped with, The laser light irradiation step is, A first step involves irradiating the substrate with the laser light along a first direction to form a plurality of modified portions within the substrate along the first direction, A second step is to irradiate the substrate with the laser light along the second direction after the first step, thereby forming a plurality of modified portions inside the substrate along the second direction. A third step is to irradiate the substrate with the laser light along the third direction after the second step, thereby forming a plurality of modified parts inside the substrate along the third direction, It has, The first step includes forming a plurality of first modified portions inside the substrate along the first direction, The second step includes forming a plurality of second modified portions inside the substrate along the second direction, The third step includes forming a plurality of third modified portions inside the substrate along the third direction, A method for manufacturing a semiconductor device, wherein the irradiation interval of the laser light in the step of forming the third modified portion is greater than the irradiation interval of the laser light in the step of forming the first modified portion and the irradiation interval of the laser light in the step of forming the second modified portion. [Section 2] The method for manufacturing a semiconductor device according to item 1, wherein the pulse energy of the laser light in the step of forming the first modified portion is greater than the pulse energy of the laser light in the step of forming the third modified portion. [Section 3] The method for manufacturing a semiconductor device according to item 2, wherein the pulse energy of the laser light in the step of forming the second modified portion is greater than the pulse energy of the laser light in the step of forming the third modified portion. [Section 4] The method for manufacturing a semiconductor device according to item 2 or 3, wherein the length of the third modified portion in the thickness direction of the substrate is longer than the length of the first modified portion in the thickness direction of the substrate. [Section 5] A method for manufacturing a semiconductor device according to any one of claims 2 to 4, wherein the length of the third modified portion in the thickness direction of the substrate is longer than the length of the second modified portion in the thickness direction of the substrate. [Section 6] In the step of forming the first modified portion, the first modified portion is formed at a first position where the distance from the second surface is a first distance, The first step described above is, Prior to the step of forming the first modified portion, a step of forming a plurality of fourth modified portions along the first direction at a second position at a second distance greater than the first distance from the second surface, The process of forming the first modified portion is followed by the process of forming a plurality of fifth modified portions along the first direction at a third position at a third distance which is less than the first distance from the second surface, It has, A method for manufacturing a semiconductor device according to any one of claims 1 to 5, wherein the irradiation interval of the laser light in the step of forming the first modified portion is smaller than the irradiation interval of the laser light in the step of forming the fourth modified portion and the irradiation interval of the laser light in the step of forming the fifth modified portion. [Section 7] The method for manufacturing a semiconductor device according to item 6, wherein the pulse energy of the laser light in the step of forming the first modified portion is greater than the pulse energy of the laser light in the step of forming the fourth modified portion and the pulse energy of the laser light in the step of forming the fifth modified portion. [Section 8] The method for manufacturing a semiconductor device according to item 7, wherein the pulse energy of the laser light in the step of forming the fifth modified portion is smaller than the pulse energy of the laser light in the step of forming the fourth modified portion. [Section 9] The method for manufacturing a semiconductor device according to item 8, wherein the irradiation interval of the laser light in the step of forming the fourth modified portion is smaller than the irradiation interval of the laser light in the step of forming the fifth modified portion.

[0098] 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]

[0099] 1...Semiconductor element, 10...Substrate, 10A...First surface, 10B...Second surface, 11...First modified section, 12...Second modified section, 13...Third modified section, 14...Fourth modified section, 15...Fifth modified section, 16...Sixth modified section, 17...Seventh modified section, 18...Eighth modified section, 19...Ninth modified section, 20...Semiconductor layer, 100...Modified section, 200...Modified section, 300...Modified section, W...Wafer

Claims

1. A step of preparing a wafer having a 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 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 having a hexagonal shape when viewed from above, Equipped with, The laser light irradiation step is, A first step involves irradiating the substrate with the laser light along a first direction to form a plurality of modified portions within the substrate along the first direction, A second step is to irradiate the substrate with the laser light along the second direction after the first step, thereby forming a plurality of modified portions inside the substrate along the second direction. A third step is to irradiate the substrate with the laser light along the third direction after the second step, thereby forming a plurality of modified portions inside the substrate along the third direction, It has, The first step includes forming a plurality of first modified portions inside the substrate along the first direction, The second step includes forming a plurality of second modified portions inside the substrate along the second direction, The third step includes forming a plurality of third modified portions inside the substrate along the third direction, A method for manufacturing a semiconductor device, wherein the irradiation interval of the laser light in the step of forming the third modified portion is greater than the irradiation interval of the laser light in the step of forming the first modified portion and the irradiation interval of the laser light in the step of forming the second modified portion.

2. The method for manufacturing a semiconductor device according to claim 1, wherein the pulse energy of the laser light in the step of forming the first modified portion is greater than the pulse energy of the laser light in the step of forming the third modified portion.

3. The method for manufacturing a semiconductor device according to claim 2, wherein the pulse energy of the laser light in the step of forming the second modified portion is greater than the pulse energy of the laser light in the step of forming the third modified portion.

4. The method for manufacturing a semiconductor device according to claim 2 or 3, wherein the length of the third modified portion in the thickness direction of the substrate is longer than the length of the first modified portion in the thickness direction of the substrate.

5. The method for manufacturing a semiconductor device according to claim 3 or claim 4, which references claim 3, wherein the length of the third modified portion in the thickness direction of the substrate is longer than the length of the second modified portion in the thickness direction of the substrate.

6. In the step of forming the first modified portion, the first modified portion is formed at a first position where the distance from the second surface is a first distance, The first step is, Prior to the step of forming the first modified portion, a step of forming a plurality of fourth modified portions along the first direction at a second position at a second distance greater than the first distance from the second surface, The process of forming the first modified portion is followed by the process of forming a plurality of fifth modified portions along the first direction at a third position at a third distance which is less than the first distance from the second surface, It has, A method for manufacturing a semiconductor device according to claim 1 or 2, wherein the irradiation interval of the laser light in the step of forming the first modified portion is smaller than the irradiation interval of the laser light in the step of forming the fourth modified portion and the irradiation interval of the laser light in the step of forming the fifth modified portion.

7. The method for manufacturing a semiconductor device according to claim 6, wherein the pulse energy of the laser light in the step of forming the first modified portion is greater than the pulse energy of the laser light in the step of forming the fourth modified portion and the pulse energy of the laser light in the step of forming the fifth modified portion.

8. The method for manufacturing a semiconductor device according to claim 7, wherein the pulse energy of the laser light in the step of forming the fifth modified portion is smaller than the pulse energy of the laser light in the step of forming the fourth modified portion.

9. The method for manufacturing a semiconductor device according to claim 8, wherein the irradiation interval of the laser light in the step of forming the fourth modified portion is smaller than the irradiation interval of the laser light in the step of forming the fifth modified portion.

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