SiC bonded substrate, and method for manufacturing a SiC bonded substrate

Abstract

The present invention provides a method for manufacturing SiC bonded substrates that can suppress the occurrence of bonding defects. The process includes: a substrate preparation step of preparing a first SiC substrate and a second SiC substrate; an activation step of irradiating the first bonding target surface of the first SiC substrate and the second bonding target surface of the second SiC substrate with an ion beam after the substrate preparation step to activate the first bonding target surface and the second bonding target surface; a bonding step of bonding the activated first bonding target surface and the second bonding target surface to obtain a SiC bonded substrate; and a heat treatment step of heat treating the SiC bonded substrate, wherein the energy per unit area of ​​the ion beam irradiated in the activation step is 0.92 J / cm². 2 More than 9.19J / cm 2 The following is a method for manufacturing a SiC bonded substrate.

Description

[Technical Field]

[0001] The present invention relates to a SiC bonded substrate and a method for manufacturing a SiC bonded substrate. [Background technology]

[0002] As one technique for bonding SiC (silicon carbide) substrates together, for example, Patent Document 1 discloses that by irradiating the bonding surface of a SiC single crystal substrate and a SiC polycrystalline or amorphous SiC substrate (which serves as a support substrate) with an inert gas ion beam, impurities adhering to the bonding surface are removed, and some of the bonding bonds that form chemical bonds of atoms exposed on a part of the bonding surface lose their bonding partners. In this state, the SiC single crystal substrate and the SiC polycrystalline or amorphous SiC substrate are bonded together by chemically bonding the bonding partners that have lost their bonding partners, thereby directly bonding two different materials. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2012-146695 [Overview of the project] [Problems that the invention aims to solve]

[0004] However, specific ion beam irradiation conditions for the substrate surface were not set, and depending on the beam conditions, foreign matter was generated from the beam source during beam irradiation and mixed into the bonding surface, resulting in bonding defects that affected various properties of the final SiC bonded substrate.

[0005] Therefore, the present invention aims to provide a SiC bonded substrate and a method for manufacturing a SiC bonded substrate that can suppress the occurrence of bonding defects. [Means for solving the problem]

[0006] To solve the above problems, the present invention provides a method for manufacturing a SiC bonded substrate, comprising: a substrate preparation step of preparing a first SiC substrate and a second SiC substrate; an activation step of irradiating a first bonding target surface of the first SiC substrate and a second bonding target surface of the second SiC substrate with an ion beam after the substrate preparation step to activate the first bonding target surface and the second bonding target surface; a bonding step of bonding the activated first bonding target surface and the second bonding target surface to obtain a SiC bonded substrate; and a heat treatment step of heat treating the SiC bonded substrate, wherein the energy per unit area of ​​the ion beam irradiated in the activation step is 0.92 J / cm². 2 More than 9.19J / cm 2 The following applies:

[0007] The angle of the irradiation direction of the ion beam may be 45° or more and 75° or less with respect to the first bonding surface and the second bonding surface, respectively.

[0008] The center of at least one of the first bonding surface and the second bonding surface may not coincide with the center of the irradiation range of the irradiated ion beam.

[0009] In the activation step, the first surface to be joined is rotated with a rotation axis perpendicular to the first surface to be joined, and the second surface to be joined is rotated with a rotation axis perpendicular to the second surface to be joined, and the rotation speed of the first surface to be joined and the second surface to be joined may be 40 rpm or more and 100 rpm or less.

[0010] Furthermore, in order to solve the above problems, the SiC bonded substrate of the present invention has a SiC single crystal substrate having a first bonding target surface and a SiC polycrystalline substrate having a second bonding target surface, and the second bonding target surface is bonded to the first bonding target surface. The first bonding target surface and the second bonding target surface are surfaces irradiated with an ion beam, and the number of particles per unit area present on the bonding surface between the first bonding target surface and the second bonding target surface is 0.4 particles / cm 2 or less.

[0011] Furthermore, in order to solve the above problems, the SiC bonded substrate of the present invention has a SiC single crystal substrate having a first bonding target surface and a SiC polycrystalline substrate having a second bonding target surface, and the second bonding target surface is bonded to the first bonding target surface. Particles are present on the bonding surface between the first bonding target surface and the second bonding target surface, and the number of the particles per unit area of the bonding surface is 0.4 particles / cm 2 or less.

[0012] Furthermore, in order to solve the above problems, the SiC bonded substrate of the present invention has a SiC single crystal substrate having a first bonding target surface and a SiC polycrystalline substrate having a second bonding target surface, and the second bonding target surface is bonded to the first bonding target surface. The number of particles per unit area present on the bonding surface between the first bonding target surface and the second bonding target surface is 0 particles / cm 2 exceeding and 0.4 particles / cm 2 or less.

Advantages of the Invention

[0013] According to the present invention, it is possible to provide a SiC bonded substrate and a method for manufacturing a SiC bonded substrate that can suppress the occurrence of bonding defects.

Brief Description of the Drawings

[0014] [Figure 1] It is a flowchart showing an example of a method for manufacturing a SiC bonded substrate. [Figure 2]This is a schematic side view of a SiC bonded substrate. [Figure 3] This is a schematic side view of the first SiC substrate on which a phosphorus-implanted layer has been formed. [Figure 4] This is a schematic side view of the first SiC substrate after hydrogen ion implantation. [Figure 5] This is a schematic diagram showing the irradiation of the first SiC substrate with an ion beam and electrons. [Figure 6] This is a schematic diagram showing how an ion beam is irradiated onto the first bonding surface 1a to remove oxide films and impurities, exposing atoms 30 and revealing bonding bonds. [Figure 7] This is a schematic diagram showing the irradiation of a second SiC substrate with an ion beam and electrons. [Figure 8A] This is a schematic diagram showing an example of the ion beam irradiation angle and the operation of the substrate placement stage during the activation process. [Figure 8B] This schematic diagram shows an example of the ion beam irradiation angle and the operation of the substrate placement stage during the activation process, which differs from Figure 8A. [Figure 8C] This schematic diagram shows an example of the ion beam irradiation angle and the operation of the substrate placement stage during the activation process, which differs from Figures 8A and 8B. [Figure 8D] This schematic diagram shows an example of the ion beam irradiation angle and the operation of the substrate placement stage during the activation process, which differs from Figures 8A to 8C. [Figure 8E] This schematic diagram shows an example of the ion beam irradiation angle and the operation of the substrate placement stage during the activation process, which differs from Figures 8A to 8D. [Figure 9] This is a schematic diagram showing the upper limit specification for etching amount. [Figure 10] This is a schematic side view of a bonded substrate formed by bonding a first SiC substrate and a second SiC substrate together. [Figure 11] This is a schematic cross-sectional view showing an example of a bonding defect (unbonded) that occurs during the manufacturing of a SiC bonded substrate. [Figure 12]This is a schematic cross-sectional view showing another example of a bonding defect (non-transfer) that occurs in the manufacturing of SiC bonded substrates. [Figure 13] This graph shows the number of particles and etching amount per substrate irradiated with the ion beam energy for the bonding surface. [Figure 14A] This graph shows the variation in the number of particles caused by changing the irradiation angle of the ion beam 8a and the position of the center 8b. [Figure 14B] This graph shows the variation in etching amount due to changes in the irradiation angle of ion beam 8a and the position of the center 8b. [Figure 15A] This graph shows the change in particle count due to changes in the rotation speed of the substrate mounting stage 13 and the irradiation angle of the ion beam 8a. [Figure 15B] This graph shows the variation in etching amount due to changes in the rotation speed of the substrate mounting stage 13 and the irradiation angle of the ion beam 8a. [Figure 16A] This graph shows the change in the number of particles due to changes in the position of the center 8b and the rotation speed of the substrate mounting stage 13. [Figure 16B] This graph shows the variation in etching amount due to changes in the position of the center 8b and the rotation speed of the substrate mounting stage 13. [Modes for carrying out the invention]

[0015] The present invention will now be described in detail with reference to the drawings, with reference to the instructions for manufacturing a SiC bonded substrate and an exemplary embodiment of the SiC bonded substrate. However, the present invention is not limited to this embodiment.

[0016] [Manufacturing method for SiC bonded substrates] Figure 1 is a flowchart showing an example of a manufacturing method for the SiC bonded substrate 100 in the present invention, and consists of a substrate preparation step, an activation step, a bonding step, and a heat treatment step. The manufacturing method for the SiC bonded substrate 100 may also include a specific element introduction step, a hydrogen ion implantation step, and a peeling step.

[0017] <Substrate preparation process> The substrate preparation process involves preparing the first SiC substrate 1 and the second SiC substrate 5, which are necessary to obtain the SiC bonded substrate 100.

[0018] The "first SiC substrate" and "second SiC substrate" used to obtain the bonded substrate do not refer to specific SiC substrates. If the "first SiC substrate" is a SiC single-crystal substrate, then the "second SiC substrate" is a SiC polycrystalline substrate. Conversely, if the "first SiC substrate" is a SiC polycrystalline substrate, then the "second SiC substrate" is a SiC single-crystal substrate. In the embodiments described later, a SiC single-crystal substrate is used for the "first SiC substrate" and a SiC polycrystalline substrate is used for the "second SiC substrate".

[0019] Figure 2 shows a schematic side view of the SiC bonded substrate 100. The SiC bonded substrate 100 shown in Figure 2 comprises a second SiC substrate 5, which is a support substrate located on the lower side, and a first SiC substrate 1, which is a SiC single crystal substrate bonded to the upper surface of the second SiC substrate 5. The first SiC substrate 1 may be formed from, for example, a single crystal substrate of a compound semiconductor (e.g., 6H-SiC, 4H-SiC, GaN, AlN). Alternatively, it may be formed from, for example, a SiC single crystal substrate of a single-element semiconductor (e.g., Si, C).

[0020] Furthermore, various materials can be used for the second SiC substrate 5. Preferably, the second SiC substrate 5 has resistance to various thermal processes applied to the first SiC substrate 1. Also, preferably, the second SiC substrate 5 is made of a material with a small difference in thermal expansion coefficient from the first SiC substrate 1. For example, when SiC is used for the first SiC substrate 1, the second SiC substrate 5 can be made of single-crystal SiC, polycrystalline SiC, single-crystal Si, polycrystalline Si, sapphire, GaN, carbon, etc.

[0021] The polycrystalline SiC described above may contain a mixture of various polytypes of SiC crystals. Since polycrystalline SiC containing various polytypes can be manufactured without strict temperature control, it is possible to reduce the cost of manufacturing the second SiC substrate 5.

[0022] (SiC polycrystalline substrate) When a SiC polycrystalline substrate is used as the second SiC substrate 5, if the thickness of the SiC polycrystalline substrate is reduced, the reinforcing effect that mitigates the warping of the SiC single crystal substrate weakens, which may result in problems such as transport errors that prevent the SiC bonded substrate from being transported. For this reason, the thickness of the SiC polycrystalline substrate is preferably 300 μm or more, and more preferably 350 μm or more. The upper limit of the thickness of the SiC polycrystalline substrate is not particularly limited and does not affect the solution of the problems of the present invention, but it can be set to, for example, 1000 μm.

[0023] The SiC polycrystalline substrate can be manufactured by depositing a film onto a graphite support substrate using a CVD method or the like. After film deposition, the graphite support substrate is removed, polished, lapped, and then the SiC single crystal substrate is transferred to produce the SiC bonded substrate 100. In particular, the thickness of the SiC polycrystalline substrate varies before and after polishing. Before polishing, the thickness is approximately 750 ± 250 μm. After lapping, the thickness is approximately 400 ± 50 μm. As the SiC polycrystalline substrate, one manufactured by the CVD method and then polished and lapped can be used.

[0024] The shape of the SiC polycrystalline substrate may be substantially the same as that of the SiC single crystal substrate. For example, it may be a disk shape with an orientation flat, and a substrate with a diameter of 100 mm to 305 mm can be used. Note that the shape is not limited to a disk shape and may be, for example, a polygonal shape. The polycrystalline SiC of the SiC polycrystalline substrate is composed of any one of 4H-SiC crystals, 6H-SiC crystals, and 3C-SiC crystals, or a mixture thereof.

[0025] (SiC single crystal substrate) When using a SiC single crystal substrate as the first SiC substrate 1, for example, a 4H-SiC single crystal substrate produced by the sublimation method can be used. The shape of the SiC single crystal substrate is, for example, a substantially disk shape with an orientation flat, and a substrate with a diameter of 100 mm to 305 mm can be used. Note that the shape is not limited to a disk shape (wafer shape) and may be, for example, a polygonal shape.

[0026] (SiC bonded substrate) The SiC bonded substrate of the embodiment includes the SiC polycrystalline substrate described above and a SiC single crystal substrate bonded to the film formation surface.

[0027] 〈Specific element introduction step〉<000019​​​​​​​​​​​​The following may also apply. Furthermore, the concentration of a specific element may be higher in regions that are 40 nm or more and 60 nm or less away from the bonding surface 4. For example, if phosphorus is implanted as the specific element, a phosphorus implantation layer 2 is formed on the first SiC substrate 1.

[0029] <Hydrogen ion implantation process> Figure 3 shows a schematic side view of the first SiC substrate 1 in which phosphorus has been implanted as a specific element, and the phosphorus implanted layer 2 has been formed. After the introduction of the specific element is complete, hydrogen ion implantation is performed on the first SiC substrate 1. When hydrogen ions are implanted into the first SiC substrate 1, the hydrogen ions reach a depth corresponding to the incident energy and are distributed at a high concentration.

[0030] Figure 4 is a schematic side view of the first SiC substrate 1 after hydrogen ion implantation. A hydrogen ion implantation section 3, indicated by a dotted line, is formed at a predetermined depth from the first bonding surface 1a. For example, the hydrogen ion implantation section 3 is formed at a depth of approximately 0.9 μm from the first bonding surface 1a.

[0031] For example, the conditions for hydrogen ion implantation include a dose of 10 14 atoms / cm 3 The above 10 16 atoms / cm 3 The acceleration voltage is between 0.1kV and 170kV. In hydrogen ion implantation, the hydrogen ion concentration may be controlled to be maximum at the first bonding surface 1a of the first SiC substrate 1.

[0032] <Activation process> Next, the activation process according to this embodiment will be described. The activation process involves irradiating the first bonding target surface 1a of the first SiC substrate 1 and the second bonding target surface 5a of the second SiC substrate 5, which were prepared in the substrate preparation process, with an ion beam 11 to activate the first bonding target surface 1a and the second bonding target surface 5a. In the activation process, electrons 12 are irradiated in addition to the ion beam 11 to the first bonding target surface 1a of the first SiC substrate 1 and the second bonding target surface 5a of the second SiC substrate 5. Hereafter, the process will be described assuming that both the ion beam 11 and electrons 12 are irradiated to the first bonding target surface 1a of the first SiC substrate 1 and the second bonding target surface 5a of the second SiC substrate 5.

[0033] In this process, for the first SiC substrate 1, as shown in Figure 5, the first SiC substrate 1 is set on the substrate placement stage 13 inside the vacuum chamber 10.

[0034] Next, the vacuum chamber 10 is evacuated. The temperature inside the vacuum chamber 10 is between 20°C and 100°C, and the vacuum level is, for example, 1.0 × 10⁻⁶. -8 Pa or more, 1.0×10 -5 Please refer to the following below Pa.

[0035] Next, the first bonding target surface 1a is irradiated with an argon (Ar) ion beam 11 and electrons 12 using an ion beam source 8 and a neutralizer 9. The argon (Ar) ion beam 11 is uniformly irradiated over the entire surface of the first bonding target surface 1a. Figure 6 shows a schematic diagram illustrating how the bonding bonds are revealed by irradiating the first bonding target surface 1a with the ion beam 11 to remove the oxide film and impurities 20 and expose the atoms 30. Figure 6(a) schematically shows atoms 30 that constitute the substrate near the first bonding target surface 1a, and oxide film and impurities 20 that schematically show the oxide film and impurities stacked on top of the atoms 30. Figure 6(b) shows the state in which the oxide film and impurities 20 are removed by irradiating them with the ion beam 11, and atoms 30 are exposed. In this way, as shown in Figure 6, the oxide film and impurities 20 of the first bonding target surface 1a can be removed, and the bonding bonds can be revealed. This state is called the activated state. Furthermore, since the irradiation with the ion beam 11 is performed in a vacuum, the first bonding target surface 1a can maintain its active state without oxidation or other processes.

[0036] Next, similar to the first SiC substrate 1, the second SiC substrate 5 is set on the substrate placement stage 13 in the vacuum chamber 10, as shown in Figure 7.

[0037] Next, the vacuum chamber 10 is evacuated. The temperature inside the vacuum chamber 10 is between 20°C and 100°C, and the vacuum level is, for example, 1.0 × 10⁻⁶. -8 Pa or more, 1.0×10 -5 Please refer to the following below Pa.

[0038] Next, the second bonding surface 5a is irradiated with an argon (Ar) ion beam 11 and electrons 12 using an ion beam source 8 and a neutralizer 9. The argon (Ar) ion beam 11 is uniformly irradiated over the entire surface of the second bonding surface 5a. This removes the oxide film and impurities 21 from the second bonding surface 5a, similar to the case of the first bonding surface 1a shown in Figure 6, exposing the bonding bonds (active state). Furthermore, since the irradiation with the ion beam 11 is performed in a vacuum, the second bonding surface 5a is not oxidized and can maintain its active state.

[0039] The beam irradiation conditions for the activation of the first bonding surface 1a and the second bonding surface 5a are calculated by combining the beam voltage, beam current, and beam irradiation time of the ion beam 11, resulting in a beam energy of 0.92 J / cm². 2 Above, 9.19J / cm 2 The following is also acceptable. This energy is calculated based on the energy irradiated from the ion beam source 8. In the activation process of this embodiment, the first bonding surface 1a and the second bonding surface 5a are irradiated with the ion beam 11 and electrons 12, respectively. However, the energy supplied to the first bonding surface 1a and the second bonding surface 5a by the irradiation of electrons 12 is sufficiently smaller than the energy supplied by the ion beam 11. Therefore, in the activation process, it is sufficient to evaluate the energy supplied to the first bonding surface 1a and the second bonding surface 5a based on the energy irradiated from the ion beam source 8. That is, a suitable range for the energy supplied to the first bonding surface 1a and the second bonding surface 5a is 0.92 J / cm², even considering the irradiation energies of both the ion beam 11 and the electrons 12. 2 Above, 9.19J / cm 2 The following applies.

[0040] Figures 8A to 8E are schematic diagrams showing the irradiation angle of the ion beam 8a and examples of the operation of the substrate placement stage 13 during the activation process. In Figures 8A to 8E, the vacuum chamber 10 and electrons 12 are not shown.

[0041] First, regarding Figure 8A, the first SiC substrate 1 is placed on the substrate mounting stage 13, and an ion beam 8a is irradiated from the ion beam source 8 onto the first bonding target surface 1a. The center 8b of the irradiation range of the ion beam 8a irradiating the first bonding target surface 1a does not coincide with the center 1b of the first bonding target surface 1a. The center 8b is moved 35 mm to the left of the center 1b (sometimes referred to as "35 mm"), and the ion beam 8a is irradiated onto the first bonding target surface 1a. Furthermore, by irradiating the first bonding target surface 1a with the ion beam 8a at an angle, the ion beam source 8 prevents oxide films and impurities 20 removed from the first bonding target surface 1a from adhering to the ion beam source 8. In addition, by tilting the substrate mounting stage 13 by 15° from the horizontal, the angle of the irradiation direction of the ion beam 8a is tilted by 45° with respect to the first bonding target surface 1a. Furthermore, by rotating the substrate mounting stage 13, the first bonding target surface 1a is rotated with a rotation axis perpendicular to the first bonding target surface 1a.

[0042] In Figure 8B, the substrate mounting stage 13 is not tilted and is positioned parallel to the horizontal direction, thereby tilting the irradiation direction of the ion beam 8a by 60° with respect to the first bonding target surface 1a. This differs from Figure 8A, except that all other conditions are the same as in Figure 8A.

[0043] In Figure 8C, the substrate mounting stage 13 is tilted 15° from the horizontal in a different direction than in Figure 8A, thereby tilting the irradiation direction angle of the ion beam 8a by 75° with respect to the first bonding target surface 1a. This is the only difference from Figure 8A; all other conditions are the same as in Figure 8A.

[0044] In Figure 8D, the center 8b of the irradiation range of the ion beam 8a irradiating the first bonding target surface 1a coincides with the center 1b of the first bonding target surface 1a. This differs from the case in Figure 8A, except that the point at which the ion beam 8a irradiates the first bonding target surface 1a is the same as in Figure 8A.

[0045] In Figure 8E, the center 8b of the irradiation range of the ion beam 8a irradiating the first bonding target surface 1a does not coincide with the center 1b of the first bonding target surface 1a. The ion beam 8a is irradiated onto the first bonding target surface 1a by shifting the center 8b 35 mm to the right of the center 1b (sometimes referred to as "-35 mm"). This is different from Figure 8A, except that all other conditions are the same as in Figure 8A.

[0046] The irradiation configurations shown in Figures 8A to 8E can be achieved by configuring the irradiation device used in the irradiation process to conform to these configurations.

[0047] As shown in Figures 8A to 8C, the angle of the irradiation direction of the ion beam 8a may be in the range of 45° to 75° with respect to the first bonding target surface 1a. By having the angle within this range, the ion beam 8a can be effectively irradiated onto the first bonding target surface 1a, and it is possible to prevent oxides and impurities 20 from adhering to the ion beam source 8, which would reduce the irradiation output or cause instability.

[0048] Similarly, for the second SiC substrate 5, the angle of the irradiation direction of the ion beam 8a may be in the range of 45° to 75° with respect to the second bonding surface 5a.

[0049] As shown in Figures 8A, 8D, and 8E, the center 8b of the irradiation range of the ion beam 8a irradiating the first bonding target surface 1a may be located within 35 mm from the center 1b of the first bonding target surface 1a. By having the center 8b within 35 mm from the center 1b, the ion beam 8a can be effectively irradiated onto the first bonding target surface 1a.

[0050] Therefore, the center 8b and the center 1b may or may not coincide. Note that the irradiation output of the ion beam 8a is strongest at the center 8b and weakens as it moves away from the center 8b. For this reason, by rotating the first bonding target surface 1a and irradiating it with the ion beam 8a in such a way that the center 8b and the center 1b do not coincide, the first bonding target surface 1a can be activated efficiently.

[0051] Similarly, for the second SiC substrate 5, the center 8b of the irradiation range of the ion beam 8a irradiating the second bonding target surface 5a may be located within 35 mm from the center 5b of the second bonding target surface 5a. By having the center 8b within 35 mm from the center 5b, the ion beam 8a can be effectively irradiated onto the second bonding target surface 5a.

[0052] Therefore, the centers 8b and 5b may or may not coincide. The irradiation output of the ion beam 8a is strongest at the center 8b and weakens as it moves away from the center 8b. For this reason, the second bonding target surface 5a can be efficiently activated by rotating the ion beam 8a and irradiating it so that the centers 8b and 5b do not coincide. In addition, the position of the center of the ion beam 8a and the center of the first bonding target surface 1a and / or the second bonding target surface 5a may be shifted (so that they do not coincide), and at the same time, the angle of the irradiation direction of the ion beam 8a may be tilted with respect to the first bonding target surface 1a and / or the second bonding target surface 5a when irradiating with the ion beam 8a.

[0053] Furthermore, as shown in Figures 8A to 8E, while the ion beam 8a is irradiated, the first bonding target surface 1a may be rotated with a rotation axis in a direction D perpendicular to the first bonding target surface 1a, and the rotation speed of the first bonding target surface 1a may be 40 rpm or more and 100 rpm or less. By rotating the first bonding target surface 1a in this way, the ion beam 8a can be irradiated evenly onto the first bonding target surface 1a, thereby enabling uniform activation of the first bonding target surface 1a.

[0054] Similarly, with respect to the second SiC substrate 5, while irradiated with the ion beam 8a, the second bonding surface 5a may be rotated with respect to a rotation axis in a direction D' perpendicular to the second bonding surface 5a, and the rotation speed of the second bonding surface 5a may be 40 rpm or more and 100 rpm or less. The rotation of each bonding surface of the first bonding surface 1a and / or the second bonding surface 5a while irradiated with the ion beam 8a can be performed simultaneously with shifting the position of the center of the ion beam 8a and the center of each bonding surface, and / or tilting the angle of the irradiation direction of the ion beam 8a with respect to the bonding surface.

[0055] The distance between the ion beam source 8 and the center 1b of the first bonding surface 1a is preferably 300 mm to 450 mm. This distance allows for effective removal of oxide films and impurities 20, thereby sufficiently activating the first bonding surface 1a. Similarly, the distance between the ion beam source 8 and the center 5b of the second bonding surface 5a is also preferably 300 mm to 450 mm.

[0056] Furthermore, if the etching amount for activating the first bonding surface 1a and the second bonding surface 5a is small (for example, if the etching amount is 0.4 nm thick), the oxide film and impurities 20 and 21 cannot be partially removed. In this case, bonding failure occurs when the number of irregularities on the first bonding surface 1a and the second bonding surface 5a exceeds 500. However, if the etching amount is large (for example, if the etching amount is 1.0 nm thick), the oxide film and impurities 20 and 21 on the first bonding surface 1a and the second bonding surface 5a can be sufficiently removed. Therefore, bonding is possible with minimal bonding failure even if the number of irregularities on the first bonding surface 1a and the second bonding surface 5a is 10,000. In other words, since the effect of the irregularities on the substrate surface can be almost ignored when the etching amount is 1.0 nm thick or more, it is preferable that the lower limit specification for the etching amount be 1.0 nm thick.

[0057] Figure 9 is a schematic diagram showing the upper limit specification for the etching amount. In the specific element introduction process, specific elements such as phosphorus are introduced into the first SiC substrate 1. In order to ensure the electrical properties of the bonding surface 4 after bonding the first SiC substrate 1 and the second SiC substrate 5, the injected layer of the specific element must remain at least 10 nm thick after etching. For example, in order for the injected layer (e.g., phosphorus injected layer 2) in which the specific element is injected at a depth of 40 nm to 60 nm from the first bonding target surface 1a to remain at least 10 nm thick, the amount of etching removed from the surface must not exceed 30 nm in thickness. In other words, it is preferable that the upper limit specification for the etching amount of the first SiC substrate 1 be 30 nm thick.

[0058] Similarly, since oxides and impurities 21 are also present on the second bonding surface 5a of the second SiC substrate 5, the lower limit specification for the etching amount may be set to a thickness of 1.0 nm and the upper limit specification to a thickness of 30 nm in order to remove them by etching. However, in the case of the second SiC substrate 5, it is sufficient to remove the oxides and impurities 21, and the injection layer is not considered, so the etching amount is not limited to these specifications.

[0059] <Joining process> Next, a bonding process according to one embodiment of the present invention will be described. The bonding process is a process of bonding a first bonding target surface 1a and a second bonding target surface 5a that have been activated by the activation process to obtain a bonded substrate 110.

[0060] In the bonding process, the first bonding surface 1a of the first SiC substrate 1 and the second bonding surface 5a of the second SiC substrate 5 are brought into contact in a vacuum chamber 10. The bonding bonds present on the first bonding surface 1a of the first SiC substrate 1 and the second bonding surface 5a of the second SiC substrate 5, which are in an activated state, connect to each other, allowing the first SiC substrate 1 and the second SiC substrate 5 to be bonded together. As a result, as shown in the schematic diagram of Figure 10, the first SiC substrate 1 and the second SiC substrate 5 are bonded together to form a bonded substrate 110.

[0061] The conditions for bonding the first SiC substrate 1 and the second SiC substrate 5 are, for example, a temperature of 20°C or higher and 100°C or lower in the vacuum chamber 10, and a vacuum degree of 1.0 × 10⁻⁶. -8 Pa or more, 1.0×10 -5 The atmosphere can be set to Pa or less. Inside the vacuum chamber 10 set to such an atmosphere, the first joining surface 1a and the second joining surface 5a are overlapped and pressed together to bond them. The first joining surface 1a and the second joining surface 5a can be pressed together under a pressure of 3000N or more and 50000N or less, and the pressing time can be 60 seconds or set to approximately 30 seconds to 5 minutes.

[0062] In the manufacturing of SiC bonded substrates 100 using substrate bonding technology, bonding defects may occur during the bonding process. Here, Figure 11 is a schematic cross-sectional view showing an example of a bonding defect (unbonded) that occurs in the manufacturing of SiC bonded substrates 100. The bonding defect shown in Figure 11 is caused by the incorporation of foreign matter a6, generated from dust from beam sources such as ion beams 8a and neutral atomic beams during surface activation, into the bonding surface 4, which is the contact area between the first SiC substrate 1 and the second SiC substrate 5. This results in a localized void where the first SiC substrate 1 and the second SiC substrate 5 are not in contact. The occurrence of a void in the bonding surface 4 may affect various properties of the final product, the SiC bonded substrate 100.

[0063] Furthermore, Figure 12 shows an example of a bonding defect different from the bonding defect shown in Figure 11. Figure 12 is a diagram showing an example of a bonding defect that occurs when large foreign matter b7, caused by dust generated by a beam source such as an ion beam 8a or a neutral atomic beam, is mixed into the bonding surface 4 of a bonding substrate 110 formed by bonding a first SiC substrate 1 and a second SiC substrate 5. The area enclosed by the dotted line that covers the foreign matter b7 indicates that a part of the first SiC substrate 1 that was removed during the bonding process would have covered the foreign matter b7 if it had not been removed. Bonding defects accompanied by damage to the first SiC substrate 1, as shown in Figure 12, occur more frequently when the first SiC substrate 1, which is the target of bonding to the second SiC substrate 5, is a thin layer. The bonding failures involving damage to the first SiC substrate 1, as shown in Figure 12, have a greater impact on the characteristics of the SiC bonded substrate 100, both in terms of the size and structure of the damaged area, compared to cases where the first SiC substrate 1 is not damaged, as shown in Figure 2. Therefore, it is particularly important to suppress their occurrence.

[0064] When foreign matter a6 and b7 generated by the beam source have a diameter exceeding 0.2 μm, poor bonding between the first SiC substrate 1 and the second SiC substrate 5 is likely to occur, with the number of foreign matter particles on the substrate surface being 0.4 particles / cm². 2 Beyond this point, bonding failures increase sharply. Specifically, the generation of foreign matter a6 and b7 with a diameter of 0.2 μm or more due to beam irradiation is 0.4 particles / cm². 2 The following needs to be suppressed.

[0065] Furthermore, if the etching amount for activating the first bonding surface 1a and the second bonding surface 5a is small (for example, if the etching amount is 0.4 nm thick), the oxide film and impurities 20 and 21 cannot be partially removed. If the first bonding surface 1a and the second bonding surface 5a are uneven and wavy, bonding failures will occur when there are 500 or more irregularities. However, if the etching amount is large (for example, if the etching amount is 1.0 nm thick), the oxide film and impurities 20 and 21 on the first bonding surface 1a and the second bonding surface 5a can be sufficiently removed. Therefore, bonding is possible with few bonding failures even if the first bonding surface 1a and the second bonding surface 5a have 10,000 irregularities. In other words, since the effect of the unevenness of the substrate surface can be almost ignored when the etching amount is 1.0 nm thick or more, it is preferable that the lower limit specification for the etching amount be 1.0 nm thick.

[0066] <Peeling process> This process involves applying heat to the bonded substrate 110 after the bonding process and before the heat treatment process, thereby forming a microbubble layer in the hydrogen ion implantation section 3, and using this microbubble layer as the peeling surface to peel off the first SiC substrate 1. In other words, the first SiC substrate 1 is peeled off from the bonded substrate 110 using the hydrogen implantation section 3, where the microbubble layer has been formed, as the peeling surface.

[0067] Specifically, the bonded substrate 110 is heated to approximately 800°C or higher. The atmosphere during delamination may be at least one of the following: an inert gas such as argon (Ar) or nitrogen (N), or a vacuum. Delamination may be performed using rapid thermal annealing (RTA) or a furnace. This allows the first SiC substrate 1 to be separated in the hydrogen ion implantation section 3. Thus, as shown in the schematic side view of Figure 2, a structure can be formed in which a thin first SiC substrate 1, for example, with a thickness of 0.9 μm, is bonded to the second SiC substrate 5 via a phosphorus implantation layer 2.

[0068] <Heat treatment process> Next, the heat treatment process according to this embodiment will be described. The heat treatment process is a process of heating and heat-treating the bonded substrate 110 after the peeling process.

[0069] The heat treatment temperature in the heat treatment process is preferably a temperature at which the introduced phosphorus is activated, and the bonded substrate 110 may be heated to 1100°C to 2200°C (preferably around 1700°C). The atmosphere for the heat treatment may be at least one of the following: an inert gas such as argon (Ar) or nitrogen (N), or a vacuum. The heat treatment process may be carried out in the furnace in which the delamination was performed. As a result, the phosphorus present in the phosphorus-implanted layer 2 moves to the bonding surface 4 between the first SiC substrate 1 and the second SiC substrate 5 and its vicinity. In this way, a SiC bonded substrate 100 is obtained by heating and heat-treating the bonded substrate 110 after the delamination process.

[0070] [SiC bonded substrate] The SiC bonded substrate comprises a SiC single-crystal substrate and a SiC polycrystalline substrate. Below, a SiC bonded substrate 100 (Figure 2) will be described as an example.

[0071] <SiC single crystal substrate> An example of a SiC single crystal substrate is a first SiC substrate 1 having a first bonding surface 1a. A phosphorus implantation layer 2 may be formed on the first SiC substrate 1.

[0072] <SiC polycrystalline substrate> An example of a SiC polycrystalline substrate is a second SiC substrate 5 having a second bonding surface 5a. The second bonding surface 5a is bonded to the first bonding surface 1a to form a bonding surface 4.

[0073] The first bonding surface 1a and the second bonding surface 5a are surfaces irradiated with an ion beam 11, for example, by an activation process, and the number of particles per unit area present on the bonding surface 4 between the first bonding surface 1a and the second bonding surface 5a is 0.4 particles / cm². 2 The following applies:

[0074] In other words, particles are present on the joining surface 4 between the first joining surface 1a and the second joining surface 5b, and the number of particles per unit area of ​​the joining surface is 0.4 particles / cm². 2 The following applies: In other words, the number of particles per unit area present on the joint surface 4 between the first joint surface 1a and the second joint surface 5b is 0 particles / cm². 2 Super and 0.4 pieces / cm 2 The following applies:

[0075] The particles are foreign matter a6 and foreign matter b7 generated by a beam source such as the ion beam source 8. When the diameter of foreign matter a6 and foreign matter b7 exceeds 0.2 μm, bonding failures between the first SiC substrate 1 and the second SiC substrate 5 are more likely to occur. In addition, the number of foreign matter a6 and foreign matter b7 present on the bonding surface 4 between the first bonding surface 1a and the second bonding surface 5a is 0.4 particles / cm. 2 Beyond this point, bonding failures increase sharply. Specifically, the generation of foreign matter a6 and b7 with a diameter exceeding 0.2 μm due to irradiation with an ion beam such as 8a is 0.4 particles / cm². 2 The following needs to be suppressed. [Examples]

[0076] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited in any way by these examples.

[0077] (Example A) In Example A, we used an ion beam irradiation device (model Combond, manufactured by EV Group) used in the manufacturing of SiC bonded substrates 100 to investigate the changes in the number of foreign particles generated and the amount of etching when the conditions of the ion beam 8a were changed. The results are summarized in Table 1.

[0078] [Test conditions] The irradiation conditions for ion beam 8a were determined by first introducing argon (Ar) gas as an inert gas into the vacuum chamber 10, and then changing the irradiation energy by varying the beam voltage, beam current, and beam irradiation time of ion beam 8a, as shown in Table 1. The substrate to be irradiated was a 3C-SiC polycrystalline substrate (hereinafter referred to as "SiC polycrystalline substrate") with a diameter of 200 mm and a circular irradiation surface free of foreign matter a6 and b7.

[0079] (Measurement of particle count) To measure the number of foreign particles (particle count in Table 1), the number of foreign particles a6 and b7 that reached the irradiated surface of the SiC polycrystalline substrate after irradiation with ion beam 8a was measured using a surface defect detection device (model Candela8520, manufactured by KLA).

[0080] (Measurement of etching amount) The thickness of the SiC polycrystalline substrate before irradiation with ion beam 8a was measured using a spectroscopic ellipsometer (model M-2000D, JAWoollam). Then, ion beam 8a irradiation was performed under the same conditions as described above, but with the irradiation conditions varied as shown in Table 1. The thickness of the SiC polycrystalline substrate after beam irradiation was measured again with a spectroscopic ellipsometer, and the difference between the average thickness of the SiC polycrystalline substrate before irradiation with ion beam 8a and the average thickness of the SiC polycrystalline substrate after irradiation was defined as the etching amount. It is assumed that if the etching conditions are the same, the etching amount will be similar for both SiC single-crystal substrates and SiC polycrystalline substrates.

[0081] (In-plane uniformity) In-plane uniformity is a parameter that indicates the uniformity of processing within a plane, and can be calculated using the following formula (1) after measuring the etching amount. For Examples A1 to A27, the in-plane uniformity on the irradiated surface was also calculated from the etching amount using formula (1).

[0082] [Formula 1] In-plane uniformity = ((Maximum in-plane etching amount - Minimum in-plane etching amount) / (2 × Average in-plane etching amount)) × 100% ... (1)

[0083] To verify the number of foreign particles and the amount of etching, as shown in Figure 8A, the angle with respect to the surface of the second SiC substrate 5, which is a SiC polycrystalline substrate, was 45°, the center of the diameter of the ion beam 8a was 35 mm from the center of the SiC polycrystalline substrate, and the SiC polycrystalline substrate rotated when irradiated with the ion beam 8a, with the rotation speed of these substrates set to 70 rpm.

[0084] [Table 1]

[0085] The graph in Figure 13 shows the number of particles and etching amount per substrate per energy irradiated by the ion beam on the bonding surface, based on the results in Table 1. In Figure 13, the in-plane average etching amount is shown as a triangular plot, and the number of particles with a characteristic length such as diameter exceeding 0.2 μm is shown as a circular plot. From the results in Figure 13, the number of foreign matter a6 and b7 is 0.4 particles / cm², which is the standard. 2 In order to satisfy both the following and the etching amount specifications of 1.0 nm or more and 30 nm or less, the energy must be 0.92 J / cm². 2 Above, 9.19J / cm 2 It was found that the following range is necessary. Specifically, if the energy of the ion beam irradiated onto the bonding surface is within this range, the adhesion of foreign substances a6 and b7 that affect bonding defects to the bonding surface can be suppressed, and oxide films and contamination on the bonding surface can be sufficiently removed, thereby obtaining the necessary activation amount immediately before bonding.

[0086] (Example B) In Example B, the energy of the ion beam 8a was set to 2.87 J / cm². 2The beam voltage was fixed at 200V, beam current at 150mA, and beam irradiation time at 30 seconds. As shown in Table 2, the SiC polycrystalline substrate was rotated by rotating the substrate mounting stage 13 during irradiation with ion beam 8a. With the substrate rotation speed set to 70rpm, the angle of the irradiation direction of ion beam 8a with respect to the irradiation surface of the SiC polycrystalline substrate was set to 45°, 60°, and 75°. The position of the substrate mounting stage 13 was adjusted so that the center 8b of the diameter of the ion beam 8a was within 35mm from the center position (1b, 5b) of the SiC polycrystalline substrate. The number of foreign matter particles and the amount of etching due to irradiation with ion beam 8a were verified using the same method as in Example A. The results are summarized in Table 2.

[0087] [Table 2]

[0088] Based on the results in Table 2, Figure 14A shows a graph illustrating the variation in the number of particles with a characteristic length exceeding 0.2 μm when the irradiation angle of ion beam 8a and the position of the center 8b are changed, and Figure 14B shows a graph illustrating the variation in the in-plane average etching amount when the irradiation angle of ion beam 8a and the position of the center 8b are changed. As shown in Figures 14A and 14B, in all examples, the foreign matter a6 and b7 met the standard of 0.4 particles / cm². 2 It was confirmed that the following etching amount specifications of 1.0 nm or more and 30 nm or less were satisfied.

[0089] (Example C) In Example C, the energy of ion beam 8a was set to 2.87 J / cm². 2The beam voltage was fixed at 200V, beam current at 150mA, and beam irradiation time at 30 seconds. The position of the substrate mounting stage 13 was adjusted so that the center 8b of the irradiation diameter of the ion beam 8a was within 35mm from the center position (1b, 5b) of the SiC polycrystalline substrate, as shown in Table 3. The angle of the irradiation direction of the ion beam 8a with respect to the irradiation surface of the SiC polycrystalline substrate was set to 45°, 60°, and 75°. The SiC polycrystalline substrate was rotated by rotating the substrate mounting stage 13 during irradiation with the ion beam 8a. The rotation speed of the substrate was varied to 40rpm, 70rpm, and 100rpm, and the number of foreign matter particles and the amount of etching due to irradiation with the ion beam 8a were verified using the same method as in Example A. The results are summarized in Table 3.

[0090] [Table 3]

[0091] Based on the results in Table 3, Figure 15A shows a graph illustrating the variation in the number of particles larger than 0.2 μm due to changes in the rotation speed of the substrate mounting stage 13 and the irradiation angle of the ion beam 8a, and Figure 15B shows a graph illustrating the variation in the in-plane average etching amount due to changes in the rotation speed of the substrate mounting stage 13 and the irradiation angle of the ion beam 8a. As shown in Figures 15A and 15B, in all examples, the foreign matter standard was 0.4 particles / cm. 2 It was confirmed that the following etching amount specifications of 1.0 nm or more and 30 nm or less were satisfied.

[0092] (Example D) In Example D, the energy of ion beam 8a was set to 2.87 J / cm². 2The beam voltage was fixed at 200V, beam current at 150mA, and beam irradiation time at 30 seconds. As shown in Table 4, the angle of the ion beam 8a irradiation direction with respect to the irradiation surface of the SiC polycrystalline substrate was set to 45°. The position of the substrate mounting stage 13 was adjusted so that the center 8b of the ion beam 8a irradiation diameter was within 35mm from the center position (1b, 5b) of the SiC polycrystalline substrate. The SiC polycrystalline substrate was rotated by rotating the substrate mounting stage 13 during irradiation with the ion beam 8a. The rotation speed of the substrate was varied to 40rpm, 70rpm, and 100rpm, and the number of foreign matter particles and the amount of etching due to irradiation with the ion beam 8a were verified using the same method as in Example A. The results are summarized in Table 4.

[0093] [Table 4]

[0094] Based on the results in Table 4, Figure 16A shows a graph illustrating the variation in the number of particles with a characteristic length exceeding 0.2 μm when the position of the center 8b and the rotation speed of the substrate mounting stage 13 are changed, and Figure 16B shows a graph illustrating the variation in the in-plane average etching amount when the position of the center 8b and the rotation speed of the substrate mounting stage 13 are changed. As a result, as shown in Figures 16A and 16B, in all examples, the foreign matter a6 and b7 met the standard of 0.4 particles / cm². 2 It was confirmed that the following etching amount specifications of 1.0 nm or more and 30 nm or less were satisfied.

[0095] As described above, based on the results of Example A, the irradiation conditions for ion beam 8a in the activation process are an energy of 0.92 J / cm². 2 More than 9.19J / cm 2 By setting the following range, it is clear that the adhesion of foreign matter a6 and b7 that affect bonding defects to the bonding surface can be suppressed, and the oxide film and contamination on the bonding surface can be sufficiently removed, thereby obtaining the necessary activation amount immediately before bonding, and it is clear that a good SiC bonded substrate 100 can be manufactured under these conditions.

[0096] Furthermore, in Examples B to D, when irradiating with the ion beam 8a, the angle of the irradiation direction of the ion beam 8a with respect to the surface of the first SiC substrate 1 and the surface of the second SiC substrate 5 is 45° or more and 75° or less, the position of the center 8b of the beam diameter is within 35 mm from the center positions (1b, 5b) of the first SiC substrate 1 and the second SiC substrate 5, and the first SiC substrate 1 and the second SiC substrate 5 rotate when irradiated with the ion beam 8a, with a rotation speed of 40 rpm or more and 100 rpm or less. It is clear that both the specifications for the number of particles (number of foreign matter a6 and b7) caused by the generation of foreign matter a6 and b7, and the specifications for the etching amount which serves as an indicator of the activation amount are satisfied, and it is clear that a good SiC bonded substrate 100 can be manufactured under these conditions. [Explanation of Symbols]

[0097] 1: First SiC substrate, 1a: First bonding surface, 1b: Center, 2: Phosphorus implantation layer, 3: Hydrogen ion implantation section, 4: Bonding surface, 5: Second SiC substrate, 5a: Second bonding surface, 5b: Center, 6: Foreign matter a, 7: Foreign matter b, 8: Ion beam source, 8a: Ion beam, 8b: Center, 9: Neutralizer, 10: Vacuum chamber, 11: Ion beam, 12: Electrons, 13: Substrate mounting stage, 20: Oxide film and impurities, 21: Oxide film and impurities, 30: Atoms, 100: SiC bonded substrate, 110: Bonded substrate

Claims

1. A substrate preparation step for preparing a first SiC substrate and a second SiC substrate, After the substrate preparation step, an activation step is performed in which an ion beam is irradiated onto the first bonding target surface of the first SiC substrate and the second bonding target surface of the second SiC substrate to activate the first bonding target surface and the second bonding target surface, A bonding step to obtain a SiC bonded substrate by bonding the first bonding target surface and the second bonding target surface in an activated state, The process includes a heat treatment step of heat-treating the SiC bonded substrate, The energy per unit area of ​​the ion beam irradiated in the activation step is 0.92 J / cm². ２ 9.19J / cm or more ２ The following is: A method for manufacturing a SiC bonded substrate.

2. The method for manufacturing a SiC bonded substrate according to claim 1, wherein the angle of the irradiation direction of the ion beam is 45° or more and 75° or less with respect to the first bonding target surface and the second bonding target surface, respectively.

3. A method for manufacturing a SiC bonded substrate according to claim 1, wherein the center of at least one of the first bonding target surface and the second bonding target surface does not coincide with the center of the irradiation range of the irradiated ion beam.

4. A method for manufacturing a SiC bonded substrate according to any one of claims 1 to 3, wherein in the activation step, the first bonding target surface is rotated with a rotation axis perpendicular to the first bonding target surface, and the second bonding target surface is rotated with a rotation axis perpendicular to the second bonding target surface, and the rotation speed of the first bonding target surface and the second bonding target surface is 40 rpm or more and 100 rpm or less.

5. A SiC single crystal substrate having a first bonding surface, The SiC polycrystalline substrate comprises a second bonding surface, the second bonding surface being bonded to the first bonding surface, The first bonding surface and the second bonding surface are surfaces irradiated with an ion beam. The number of particles per unit area present on the joint surface between the first and second surfaces to be joined is 0.4 particles / cm². ２ The following is a SiC bonded substrate.

6. A SiC single crystal substrate having a first bonding surface, The SiC polycrystalline substrate comprises a second bonding surface, the second bonding surface being bonded to the first bonding surface, Particles are present on the joining surface between the first joining surface and the second joining surface, and the number of particles per unit area of ​​the joining surface is 0.4 particles / cm². ２ The following is a SiC bonded substrate.

7. A SiC single crystal substrate having a first bonding surface, The SiC polycrystalline substrate comprises a second bonding surface, the second bonding surface being bonded to the first bonding surface, The number of particles per unit area present on the joint surface between the first joint target surface and the second joint target surface is 0 particles / cm². ２ Super high, 0.4 pieces / cm ２ The following is a SiC bonded substrate.

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