Composite substrate, device, and method for manufacturing composite substrate

Abstract

A composite substrate 1 comprises: a functional layer 21a; a support substrate 23 that supports the functional layer 21a; a first coating layer 22a that is provided between the functional layer 21a and the support substrate 23; a beveling region 12 that, in an outer peripheral section, is formed from the functional layer 21a to a portion of the support substrate 23; and a second cover layer 22b that covers respective side surfaces of the functional layer 21a and the first cover layer 22a and a main surface on the functional layer 21a side of the support substrate 23. In such a case, it is preferable to further comprise a third cover layer 22c that covers a main surface on the side opposite of that of the main surface on the functional layer 21a side of the support substrate 23. The present invention thereby provides, inter alia, a composite substrate in which damage to the support substrate is unlikely to occur when, inter alia, polishing the functional layer, even if beveling is performed.

Description

Composite substrate, device, and method for manufacturing a composite substrate

[0001] The present invention relates to composite substrates, devices, and methods for manufacturing composite substrates. In particular, the present invention relates to composite substrates having a beveled region on the outer periphery.

[0002] It is known that when fabricating composite substrates, the unadhered region formed at the wafer edge can be removed by beveling the outer edge of the composite substrate in a circular pattern during the fabrication process, thereby suppressing the peeling of the thin film from the unadhered region.

[0003] Patent Document 1 describes a semiconductor substrate having a semiconductor layer on a support, wherein at least the outer edge of the semiconductor layer is located inward from the outer edge of the support, and at least the periphery of the side of the semiconductor layer opposite to the support is chamfered.

[0004] Japanese Patent Application Publication No. 1-227441

[0005] However, in conventional composite substrates where the outer periphery is ground, the support substrate is exposed as a result of beveling. In this case, for example, when processing the functional layer by polishing, etching, or ion implantation, damage occurs to the exposed portion of the support substrate, resulting in contamination such as chipping or peeling. As a result, yield decreases and device performance deteriorates. The present invention aims to provide a composite substrate that, even when beveling is performed, is less prone to damage to the support substrate and contamination such as chipping or peeling that occurs when polishing the functional layer.

[0006] To solve the above problems, the present invention provides a composite substrate comprising: a functional layer; a support substrate for supporting the functional layer; a first coating layer provided between the functional layer and the support substrate; a beveling region formed on the outer periphery, extending from the functional layer to a portion of the support substrate; and a second coating layer covering the respective side surfaces of the functional layer and the first coating layer, as well as the main surface of the support substrate on the functional layer side, within the beveling region. The present invention also provides a device comprising the above composite substrate. Furthermore, the present invention provides a method for manufacturing a composite substrate, comprising: a coating layer formation step of forming a coating layer that covers the entire circumferential surface of a support substrate that supports a functional layer; a bonding step of bonding a functional layer wafer, which will be the basis of the functional layer, and a support substrate via the coating layer; a beveling step of performing beveling from the functional layer wafer to a part of the support substrate on the outer periphery of the bonded functional layer wafer and support substrate to form a beveled region and forming a first coating layer to be provided between the functional layer and the support substrate; a second coating layer formation step of forming a second coating layer that covers the respective side surfaces of the functional layer wafer and the first coating layer, and the main surface of the support substrate on the functional layer wafer side, in the beveled region; and a polishing step of polishing the functional layer wafer after the second coating layer formation step to form a functional layer. Furthermore, the present invention provides a method for manufacturing a composite substrate, comprising: a coating layer formation step of forming a coating layer that covers the entire circumferential surface of a support substrate that supports a functional layer; a bonding step of bonding a functional layer wafer, which will be the basis of the functional layer, to a support substrate; a beveling step of performing beveling from the functional layer wafer to a part of the support substrate on the outer periphery of the bonded functional layer wafer and support substrate to form a beveled region and forming a first coating layer to be provided between the functional layer and the support substrate; a polishing step of polishing the functional layer wafer to form a functional layer; and a second coating layer formation step, after the polishing step, of forming a second coating layer that covers the functional layer, the side surface of the first coating layer, and the main surface of the support substrate on the functional layer wafer side in the beveled region.

[0007] The objective is to provide composite substrates that are less prone to damage to the support substrate when beveling or polishing the functional layer.

[0008] Figures illustrating the composite substrate of this embodiment. (a) to (b) are figures illustrating the composite substrate of this embodiment. (a) to (b) are figures illustrating a conventional composite substrate. Figures illustrating modified versions of the composite substrate in this embodiment. Figures illustrating other modified versions of the composite substrate in this embodiment. (a) to (i) are figures illustrating the manufacturing method of the composite substrate shown in Figure 2(a). (a) to (i) are figures illustrating the manufacturing method of the composite substrate shown in Figure 5.

[0009] The embodiments of the present invention will be described in detail below with reference to the attached drawings.

[0010] <Description of the Composite Substrate Configuration> Figures 1 and 2(a) to 2(b) show the composite substrate 1 of this embodiment. Of these, Figure 1 is a top view of the composite substrate 1, and Figure 2(a) is a cross-sectional view of Figure 1 taken along the line IIa-IIa, schematically showing the layer structure of the composite substrate 1. Figure 2(b) is a diagram that further describes the outer periphery of the composite substrate 1 in detail. As shown in Figure 1, the composite substrate 1 has a substantially circular shape with an orientation flat (orifura) portion 11. The orientation flat portion 11 is a planar portion formed on the side surface of the composite substrate 1 to indicate the crystal orientation of the composite substrate 1. The composite substrate 1 has an outer diameter of, for example, 4 inches or more and 12 inches or less, and a thickness of, for example, 200 μm or more and 1000 μm or less. The composite substrate 1 also has a beveling region 12 on its outer periphery. Here, "outer periphery" refers to the edge when the composite substrate 1 is viewed from above. The beveling region 12 is formed by chamfering the outer periphery of the composite substrate 1. This suppresses sagging of the outer periphery when forming the functional layer 21a of the composite substrate 1. The region other than the beveling region 12, which is inside the beveling region 12, is the effective region 13 that is used when actually fabricating the device.

[0011] Furthermore, as shown in Figures 2(a) to 2(b), the composite substrate 1 has a structure in which a functional layer 21a, a first coating layer 22a, and a support substrate 23 are stacked from the top in the figure. The composite substrate 1 also has a second coating layer 22b in the beveling region 12 and a third coating layer 22c on the lower surface of the support substrate 23.

[0012] The functional layer 21a is selected for the application in which the composite substrate 1 is used. The functional layer 21a is made of, for example, a piezoelectric material. The piezoelectric material is, for example, lithium niobate (LiNbO3(LN)), lithium tantalate (LiTaO3(LT)), or a solid solution of lithium niobate and lithium tantalate. In this case, the direction normal to the main surface of the functional layer 21a is such that the functional layer 21a is LiNbO ３ When consisting of (LN), it is preferable to use one that is rotated 37.8° from the Z-axis to the -Y-axis around the X-axis, which is the propagation direction of the surface acoustic wave, i.e., one that is (0°, 37.8°, 0°) in Euler angle notation, because it results in a large electromechanical coupling coefficient. Also, if the functional layer 21a is LiTaO ３ When (LT) is used, it is preferable to use a configuration that is rotated 32° to 50° from the Y axis to the Z axis around the X axis, which is the propagation direction of the surface acoustic wave, i.e., (180°, 58° to 40°, 180°) in Euler angle notation, because the propagation loss is small. Note that the materials used for the functional layer 21a are not limited to these, and quartz, sapphire, gallium arsenide (GaAs), silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), solid solution ceramics (PZT), etc., can be appropriately selected.

[0013] The thickness of the functional layer 21a can be, for example, set to a lower limit of 100 nm or more, preferably 300 nm or more, and an upper limit of 20,000 nm or less, preferably 2,000 nm or less. The thickness of the functional layer 21a is set appropriately according to the function that the functional layer 21a is to perform.

[0014] The first coating layer 22a is provided between the functional layer 21a and the support substrate 23. It can also be said that the first coating layer 22a is an intermediate layer provided between the functional layer 21a and the support substrate 23. The first coating layer 22a is determined by the combination of the functional layer 21a and the support substrate 23. According to the combination of the functional layer 21a and the support substrate 23, silicon oxide (SiO₂) ２ ), tantalum pentoxide (Ta ２ O ５ ), silicon carbonitride (SiCN) can be used. Also, depending on the combination of the functional layer 21a and the support substrate 23, niobium oxide (Nb) can be used.２ O ５ ), aluminum oxide (Al ２ O ３ ), aluminum nitride (AlN), silicon nitride (Si ３ N ４ ), hafnium oxide (HfO ２ ), etc., can also be used.

[0015] The first coating layer 22a may have a thickness (T) of, for example, 1 µm or more and 30 µm or less. If the thickness (T) between the functional layer 21a and the supporting substrate 23 is less than 1 µm, exposed portions are likely to occur on the supporting substrate 23. In addition, if the thickness (T) between the functional layer 21a and the supporting substrate 23 exceeds 30 µm, the functional performance of the functional layer 21a is prone to degradation.

[0016] The supporting substrate 23 serves as a support for the entire composite substrate 1. The supporting substrate 23 is covered by the first coating layer 22a and supports the functional layer 21a and the first coating layer 22a. Any appropriate substrate can be used as the supporting substrate 23. The supporting substrate 23 may be composed of a single crystal, may be composed of a polycrystal, or may be a composite obtained by providing a polycrystalline layer on a single crystal.

[0017] Preferred materials for constituting the supporting substrate 23 are silicon (Si), glass, sapphire, quartz glass, crystal, and silicon carbide (SiC). However, the material is not limited thereto, and may be sialon, cordierite, mullite, alumina, SUS, iron-nickel alloy (42 alloy), brass, or the like. The outer diameter of the supporting substrate 23 is, for example, 4 inches or more and 12 inches or less, and the thickness thereof is, for example, 200 µm or more and 1000 µm or less, but any other appropriate thickness can be adopted. When the supporting substrate 23 is made of silicon (Si), it is preferable that the resistivity is 1000 Ω / m or more. This improves RF (Radio Frequency) characteristics when the composite substrate 1 is used for manufacturing high-frequency devices such as surface acoustic wave filters (SAW (Surface Acoustic Wave) filters) and optical modulators.

[0018] As shown in Figures 2(a) to (b), the beveling region 12 is formed on the outer periphery of the composite substrate 1, extending from the functional layer 21a to a part of the support substrate 23. In other words, the beveling region 12 is formed by removing the entire outer periphery of the functional layer 21a and the first coating layer 22a in the thickness direction, and for the outer periphery of the support substrate 23, removing a part of the upper part in the thickness direction as shown in the figure, while leaving the lower part as is. The beveling region 12 may be stepped or curved. Furthermore, it may be inclined or may be a stepped shape composed of multiple steps. Among these, the stepped shape shown in Figures 2(a) to (b) is preferred. That is, the beveling region 12 is formed by removing a rectangular portion of the functional layer 21a, the first coating layer 22a, and the support substrate 23, resulting in the stepped shape shown. As shown in Figure 2(b), if the beveling width is defined as the width of the beveling region 12, the beveling width can be 1 mm or more and 4 mm or less. If the beveling width is less than 1 mm, an unadhered area is likely to remain on the outer periphery. On the other hand, if the beveling width exceeds 4 mm, the usable effective area 13 as a device is reduced too much. Furthermore, if the beveling depth is defined as the amount of material removed in the stacking direction of the functional layer 21a, the first coating layer 22a, and the support substrate 23, it is preferable that the beveling depth be 1 μm or more. If the beveling depth is less than 1 μm, the functional layer 21a may not be sufficiently removed.

[0019] The second coating layer 22b covers the sides of the functional layer 21a and the first coating layer 22a, respectively, and the main surface of the support substrate 23 on the functional layer 21a side in the beveling region 12. The third coating layer 22c covers the main surface of the support substrate 23 on the opposite side from the main surface of the functional layer 21a side. In other words, the second coating layer 22b and the third coating layer 22c ensure that no part of the support substrate 23 is exposed. The second coating layer 22b and the third coating layer 22c are made of the same material as the first coating layer 22a. For example, the first coating layer 22a is made of silicon oxide (SiO₂ ２ If the second coating layer 22b and the third coating layer 22c are made of silicon oxide (SiO2), then the second coating layer 22b and the third coating layer 22c are made of silicon oxide (SiO2). ２ ) consists of.

[0020] The second coating layer 22b can have a thickness of 0.1 μm or more and less than or equal to the beveling depth. By making the thickness of the second coating layer 22b 0.1 μm or more, the difference in film thickness between the effective region 13 and the beveling region 12 can be reduced, mitigating the film stress difference and suppressing chipping and cracking. On the other hand, if the thickness of the second coating layer 22b exceeds the beveling depth, the height of the beveling region 12 will be higher than the surface of the functional layer 21a, which will hinder uniform processing in subsequent processes such as device formation. Furthermore, the third coating layer 22c can have approximately the same thickness as the first coating layer 22a, for example. As will be described in more detail later, the first coating layer 22a and the third coating layer 22c are silicon oxide (SiO ２ In this case, the first coating layer 22a and the third coating layer 22c can both be formed in a process of thermal oxidation of silicon (Si). In this case, the third coating layer 22c will have approximately the same thickness as the first coating layer 22a.

[0021] Figures 3(a) and 3(b) show a conventional composite substrate. Of these, the composite substrate 2 shown in Figure 3(a) has a structure in which a functional layer 21a, an intermediate layer 22A, and a support substrate 23 are laminated. The intermediate layer 22A is made of the same material as the first coating layer 22a. Compared to the composite substrate 1 shown in Figure 2(a), the composite substrate 2 shown in Figure 3(a) lacks the second coating layer 22b and the third coating layer 22c. In this case, because the second coating layer 22b is absent, the support substrate 23 is exposed by the beveling region 12.

[0022] Furthermore, the composite substrate 3 shown in Figure 3(b) has a structure in which a functional layer 21a, a first coating layer 22a, a support substrate 23, and a third coating layer 22c are laminated, similar to the composite substrate 1 shown in Figure 2(a). On the other hand, the composite substrate 2 shown in Figure 3(b) lacks the second coating layer 22b compared to the composite substrate 1 shown in Figure 2(a). In this case as well, similar to the case in Figure 3(a), because the second coating layer 22b is absent, the support substrate 23 is exposed by the beveling region 12.

[0023] In the structures shown in Figures 3(a) and 3(b), the beveling region 12 exposes the support substrate 23, making it susceptible to damage to the exposed portion of the support substrate 23 when polishing the functional layer 21a, for example. In this case, contamination caused by the damage leads to a decrease in yield when processing the functional layer 21a by polishing, etching, ion implantation, etc. In the composite substrate 1 shown in Figure 2(a), a second coating layer 22b and a third coating layer 22c are provided, covering the support substrate 23 without exposing it. This suppresses damage when polishing the functional layer 21a, for example. As a result, yield reduction and degradation of element performance are less likely to occur around the exposed portion of the support substrate 23.

[0024] For example, when polishing the functional layer 21a, damage is most likely to occur around the beveling region 12, so it is not necessarily required to provide a third coating layer 22c formed in the area excluding this region.

[0025] Figure 4 shows a modified example of the composite substrate 1 in this embodiment. The composite substrate 1 shown in Figure 4 lacks the third coating layer 22c compared to the composite substrate 1 shown in Figure 2(a). As a result, the beveling region 12 of the support substrate 23 is covered by the second coating layer 22b, making the aforementioned damage less likely to occur. However, it is more preferable to have a third coating layer 22c, as shown in Figure 2(a), so that the entire circumferential surface of the support substrate 23 is covered by the second coating layer 22b and the third coating layer 22c. This makes it possible to suppress deformation of the composite substrate 1 due to film stress.

[0026] Figure 5 shows another modified example of the composite substrate 1 in this embodiment. Compared to the composite substrate 1 shown in Figure 2(a), the composite substrate 1 shown in Figure 5 has a second coating layer 22b provided not only on the side surface of the functional layer 21a but also on the top surface of the functional layer 21a. This can also be said to mean that the second coating layer 22b covers not only the beveling region 12 but also the main surface of the functional layer 21a opposite to the main surface on the side where the first coating layer 22a is provided. As a result, the entire exposed portion of the functional layer 21a is covered with the second coating layer 22b, which prevents damage to the functional layer 21a from being caused by etching during device formation.

[0027] In the above-described configuration, by forming a second coating layer 22b on the support substrate 23, the support substrate 23 is not exposed, and damage to the support substrate 23 can be suppressed.

[0028] <Device> The structure of the composite substrate 1 shown in the figure can be used as the structure of various devices. Examples of devices include high-frequency devices, power semiconductors, semiconductor lasers, surface acoustic wave filters (SAW filters), optical modulation devices, thin-film piezoelectric MEMS (Micro Electro Mechanical Systems), etc.

[0029] <Explanation of the manufacturing method of the composite substrate 1> Next, the manufacturing method of the composite substrate 1 will be explained. Figures 6(a) to 6(i) are diagrams illustrating the manufacturing method of the composite substrate 1 shown in Figure 2(a). First, a functional layer wafer 21 and a support substrate 23, which will be the basis of the functional layer 21a, are prepared (1. Substrate preparation step, Figure 6(a)). Here, as the functional layer wafer 21, a substrate with a diameter of 4 inches or more and 12 inches or less, and a thickness of 100 μm or more and 500 μm or less is prepared. Also, as the support substrate 23, a substrate with the same diameter as the functional layer wafer 21 and a thickness of 100 μm or more and 2000 μm or less is prepared (substrate preparation step). Here, the functional layer wafer 21 is assumed to be LN, and the support substrate 23 is assumed to be Si.

[0030] Next, the support substrate 23 is thermally oxidized to form a coating layer 22 on the entire circumferential surface of the support substrate 23 (2. Thermal oxidation process, Figure 6(b)). Here, the surface of the support substrate 23, which is made of Si, is oxidized, and SiO２ A coating layer 22 is formed, consisting of the above. The coating layer 22 is the base layer for the first coating layer 22a and the third coating layer 22c. Dry oxygen is used as the oxidizing atmosphere when performing thermal oxidation (dry oxidation), but if necessary, water vapor (wet oxidation) or oxygen with hydrochloric acid (hydrochloric acid oxidation) added may be used. The coating layer 22 is made to be between 5 μm and 20 μm in thickness.

[0031] Furthermore, the main surface that will become the bonding surface between the functional layer wafer 21 and the coating layer 22 is polished (3. Bonding surface polishing process, Figure 6(c)). Here, the bonding surface is polished so that the arithmetic mean height (Sa) is 1.0 nm or less. This improves the bonding strength in the subsequent 4. Bonding process. It is even more preferable to make the arithmetic mean height (Sa) 0.2 nm or less. Making the arithmetic mean height (Sa) 0.2 nm or less significantly improves the bonding strength. Figure 6(c) shows the case where the arithmetic mean height (Sa) is 0.2 nm.

[0032] Next, the bonding surfaces of the functional layer wafer 21 and the coating layer 22 are bonded (4. Bonding process, Figure 6(d)). The bonding method is not particularly limited and can be performed by, for example, surface activated bonding (SAB) or plasma activated bonding (PAB), but plasma activated bonding (PAB) is preferred. In the case of plasma activated bonding, a plasma activation treatment is performed to activate at least one of the bonding surfaces of the functional layer wafer 21 and the coating layer 22 with plasma. Examples of gases used to generate plasma include Ar and O. ２ , N ２ , H ２ O, H ２ And combinations thereof are examples. In this case, for example, the pressure during activation is set to 1 Pa or more and 100 Pa or less, and the temperature is set to 30°C or more and 100°C or less. The plasma irradiation energy is set to 100 W or more and 500 W or less. The bonding is carried out in atmospheric pressure or in a vacuum. When bonding in a vacuum, the pressure is 1.0 × 10⁻⁶ －７ Pa or more 1.0×10 ２Set the pressure within the range below Pa. Then, bring the respective bonding surfaces into contact with each other and press them with a predetermined pressure. Thereby, the functional layer wafer 21 and the support substrate 23 are bonded via the covering layer 22.

[0033] Then, grind the main surface opposite to the bonding surface of the functional layer wafer 21 (5. Grinding step, Fig. 6(e)). In this case, the functional layer wafer 21 is thinned to a thickness of 3 µm to 30 µm. Grinding can be performed by a known method using a grinding machine. In Fig. 6(e), the portion to be removed by grinding is indicated by a dotted line.

[0034] Next, heat the bonded functional layer wafer 21 and the support substrate 23 (6. Heating step, Fig. 6(f)). The heating is performed, for example, at a temperature of 100°C to 250°C for 1 hour to 10 hours.

[0035] Furthermore, the outer peripheral portion of the functional layer wafer 21 and the support substrate 23 bonded via the covering layer 22 is ground from the functional layer wafer 21 to a part of the support substrate 23 to form the beveling region 12 (7. Outer peripheral portion grinding step, Fig. 6(g)). At this time, the beveling width is set to 1 mm to 4 mm, and the roughness after grinding is set to 100 nm to 500 nm in terms of arithmetic average height (Sa). Grinding can be performed, for example, by a grinding device in which a disc-shaped grinding wheel is rotated at a high speed, and the grinding wheel is moved along the side surfaces while being in contact with the side surfaces of the functional layer wafer 21 and the support substrate 23 to grind the outer peripheral portion. In Fig. 6(g), the portion to be removed by grinding is indicated by a dotted line. Then, as a result of the grinding, a first covering layer 22a and a third covering layer 22c are formed.

[0036] Next, form the second covering layer 22b at the position of the beveling region 12 (8. Second covering layer forming step, Fig. 6(h)). At this time, the arrangement is carried out such that the second covering layer 22b is formed on the effective region 13 of the functional layer 21a and the beveling region 12. The method for forming the second covering layer 22b is not particularly limited, and any film forming method such as sputtering film formation, ion-assisted film formation, CVD (Chemical Vapor Deposition) may be used. The thickness of the second covering layer 22b is set to 0.1 µm to 5 µm.

[0037] Then, the main surface of the functional layer wafer 21 is polished to the desired thickness to form the functional layer 21a (9. Polishing (thinning) step, Figure 6(i)). The thickness of the functional layer 21a at this time is set to be between 100 nm and 2000 nm. Polishing can be performed by a known method using a polishing machine. In Figure 6(i), the areas to be removed by polishing are shown by dotted lines. This makes it possible to manufacture the composite substrate 1 shown in Figure 2(a). Note that steps 8. Second coating layer formation step (Figure 6(h)) and 9. Polishing (thinning) step (Figure 6(i)) may be reversed. In this case, the composite substrate 1 shown in Figure 5 can be manufactured.

[0038] Figures 7(a) to 7(i) illustrate the manufacturing method of the composite substrate 1 shown in Figure 5. Figures 7(a) to 7(g) are the same as Figures 6(a) to 7(g). After Figure 7(g), the main surface of the functional layer wafer 21 is polished to the desired film thickness to form the functional layer 21a (8. Polishing (thinning) process, Figure 7(h)).

[0039] Next, a second coating layer 22b is formed on the functional layer 21a and the beveling region 12 (9. Second coating layer formation step, Figure 7(i)). This makes it possible to manufacture a composite substrate 1 as shown in Figure 5.

[0040] The manufacturing method of the composite substrate 1 shown in Figure 6 above comprises a coating layer formation step (corresponding to the thermal oxidation step described above) in which a coating layer 22 is formed to cover the entire circumferential surface of the support substrate 23 that supports the functional layer 21a, a bonding step in which the functional layer wafer 21 which will be the basis of the functional layer 21a is bonded to the support substrate 23, and a beveling step in which beveling is performed on the outer periphery of the bonded functional layer wafer 21 and support substrate 23 from the functional layer wafer 21 to a part of the support substrate 23 to form a beveled region 12, and a part provided between the functional layer 21a and the support substrate 23 This can be understood as a method for manufacturing a composite substrate, comprising: a beveling step to form a first coating layer 22a (corresponding to the outer peripheral grinding step described above); a second coating layer formation step to form a second coating layer 22b in the beveling region 12 that covers the respective sides of the functional layer wafer 21 and the first coating layer 22a, and the main surface of the support substrate 23 on the functional layer wafer 21 side; and a polishing step after the second coating layer formation step to polish the functional layer wafer 21 to form a functional layer 21a (corresponding to the polishing (thinning) step described above).

[0041] Furthermore, the manufacturing method of the composite substrate 1 shown in Figure 7 above comprises a coating layer formation step (corresponding to the thermal oxidation step described above) in which a coating layer 22 is formed to cover the entire circumferential surface of the support substrate 23 that supports the functional layer 21a, a bonding step in which the functional layer wafer 21 which will be the basis of the functional layer 21a is bonded to the support substrate 23, and in the outer periphery of the bonded functional layer wafer 21 and support substrate 23, beveling is performed from the functional layer wafer 21 to a part of the support substrate 23 to form a beveled region 12, and the functional layer 21a and the support substrate 23 This can be understood as a method for manufacturing a composite substrate, comprising: a beveling step (corresponding to the outer peripheral grinding step described above) for forming a first coating layer 22a provided in between; a polishing step (corresponding to the polishing (thinning) step described above) for polishing the functional layer wafer 21 to form a functional layer 21a; and a second coating layer formation step, after the polishing step, for forming a second coating layer 22b in the beveling region 12 that covers the functional layer 21a, the side surface of the first coating layer 22a, and the main surface of the support substrate 23 on the functional layer wafer 21 side.

[0042] In the manufacturing method of the composite substrate 1 shown in Figures 6 and 7 above, a second coating layer 22b is formed on the support substrate 23 in the second coating layer formation step. This prevents the support substrate 23 from being exposed and makes it possible to provide a composite substrate 1 that suppresses damage to the support substrate 23.

[0043] Furthermore, the manufacturing method of the composite substrate 1 is not limited to the above-described form. For example, the functional layer 21a can be formed by forming a thin film by ion implantation. This is a technique for transferring a thin film from the functional layer wafer 21 to the support substrate 23. Specifically, light ions are implanted into the functional layer wafer 21 at an arbitrary depth to form a fragile layer (ion implantation step). Then, after bonding with the support substrate 23 via the coating layer 22, the fragile layer is peeled off by heating and transferred as the functional layer 21a (transfer step). The ion implantation energy is adjusted so that spontaneous separation occurs by applying heat treatment at an appropriate temperature after bonding.

[0044] (Example 1) In Example 1, the composite substrate 1 of this embodiment was manufactured by the method shown in Figures 6(a) to (i). A lithium niobate substrate (LN substrate) with a diameter of 4 inches and a thickness of 250 μm was prepared as the functional layer wafer 21 which would form the basis of the functional layer 21a. In addition, a Si substrate with the same diameter as the functional layer wafer 21 and a thickness of 500 μm was prepared as the support substrate 23 (substrate preparation step).

[0045] Next, the support substrate 23 is thermally oxidized, and SiO ２ A coating layer 22 made of the above material was formed on the entire circumferential surface of the support substrate 23 (thermal oxidation process). In this process, the support substrate 23 was thermally oxidized using water vapor (wet oxidation) to make the coating layer 22 10 μm thick. The coating layer 22 on the side surfaces of the support substrate 23 was also made 10 μm thick.

[0046] Furthermore, the main surface that would become the bonding surface between the functional layer wafer 21 and the coating layer 22 was polished (bonding surface polishing step). Here, the bonding surface was polished so that the arithmetic mean height (Sa) was 0.2 nm. Next, the bonding surfaces of the functional layer wafer 21 and the coating layer 22 were bonded (bonding step). Here, bonding was performed in a chamber by plasma-activated bonding (PAB). At this time, H was used as the gas for the plasma activation treatment. ２ Using oxygen (O), the chamber pressure during activation was set to 5 Pa, the plasma irradiation energy to 400 W, and the chamber temperature to 40°C. The bonding was then performed in a vacuum at a pressure of 100 Pa.

[0047] Next, the main surface of the functional layer wafer 21 opposite to the bonding surface was ground to create a thin film (grinding step). In this case, the film was thinned to a thickness of 30 μm. Then, the bonded functional layer wafer 21 and the support substrate 23 were heated (heating step). Heating was performed using a clean oven at a temperature of 150°C for 10 hours.

[0048] Furthermore, the unbonded area on the outer periphery was removed by grinding to form a beveled area 12 (outer periphery grinding process). At this time, the beveling width was set to 2 mm, and the roughness after grinding was set to an arithmetic mean height (Sa) of 100 nm. Then, SiO was applied to the beveled area 12. ２ A second coating layer 22b was formed (second coating layer formation step). Here, the film was formed by CVD. The thickness of the second coating layer 22b was 0.1 μm. Finally, the main surface of the functional layer wafer 21 was polished to the desired thickness to form the functional layer 21a (polishing (thinning) step). The thickness of the functional layer 21a was set to 500 nm. Thus, the composite substrate 1 of this embodiment was manufactured.

[0049] (Comparative Example 1) A composite substrate was manufactured in the same manner as in Example 1, except that the second coating layer formation step was omitted and the second coating layer 22b was not formed.

[0050] (Results) In Example 1, it was confirmed that no peeling occurred between the functional layer 21a and the support substrate 23, and that the outer peripheral removal surface was the coating layer 22. It was also confirmed that no damage occurred to the support substrate 23. In contrast, in Comparative Example 1, damage sometimes occurred to the support substrate 23.

[0051] Although this embodiment has been described above, the technical scope of the present invention is not limited to the scope described in the above embodiment. It is clear from the claims that various modifications or improvements made to the above embodiment are also included in the technical scope of the present invention.

[0052] 1...Composite substrate, 12...Beveling region, 21...Functional layer wafer, 21a...Functional layer, 22...Coating layer, 22a...First coating layer, 22b...Second coating layer, 22c...Third coating layer, 23...Support substrate

Claims

1. A composite substrate comprising: a functional layer; a support substrate for supporting the functional layer; a first coating layer provided between the functional layer and the support substrate; a beveling region formed on the outer periphery, extending from the functional layer to a portion of the support substrate; and a second coating layer covering the respective side surfaces of the functional layer and the first coating layer, and the main surface of the support substrate on the functional layer side, within the beveling region.

2. The composite substrate according to claim 1, further comprising a third coating layer that covers the main surface of the support substrate opposite to the main surface on the functional layer side.

3. The composite substrate according to claim 1, wherein the second coating layer further covers the main surface of the functional layer opposite to the main surface on which the first coating layer is provided.

4. The composite substrate according to claim 1, wherein the second coating layer has a thickness of 0.1 μm or more and 5 μm or less.

5. The composite substrate according to claim 1, wherein the first coating layer has a thickness of 1 μm or more and 30 μm or less.

6. The functional layer is LiNbO ３ (LN), LiTaO ３ The composite substrate according to claim 1, comprising any one of (LT), solid solution ceramics, quartz, sapphire, and silicon carbide (SiC).

7. The support substrate is silicon (Si), and the first coating layer and the second coating layer are silicon oxide (SiO ２ The composite substrate according to claim 1, which is the composite substrate described in claim 1.

8. The composite substrate according to claim 6, wherein the resistivity of the support substrate, which is silicon (Si), is 1000 Ω / m or more.

9. A device comprising a composite substrate according to any one of claims 1 to 8.

10. A method for manufacturing a composite substrate, comprising: a coating layer formation step of forming a coating layer that covers the entire circumferential surface of a support substrate that supports a functional layer; a bonding step of bonding a functional layer wafer that will be the basis of the functional layer to the support substrate; a beveling step of performing beveling from the functional layer wafer to a part of the support substrate on the outer periphery of the bonded functional layer wafer and the support substrate to form a beveled region and forming a first coating layer to be provided between the functional layer and the support substrate; a second coating layer formation step of forming a second coating layer that covers the respective side surfaces of the functional layer wafer and the first coating layer, and the main surface of the support substrate on the functional layer wafer side in the beveled region; and a polishing step of polishing the functional layer wafer after the second coating layer formation step to form the functional layer.

11. A method for manufacturing a composite substrate, comprising: a coating layer formation step of forming a coating layer that covers the entire circumferential surface of a support substrate that supports a functional layer; a bonding step of bonding a functional layer wafer that will be the basis of the functional layer to the support substrate; a beveling step of performing beveling from the functional layer wafer to a part of the support substrate on the outer periphery of the bonded functional layer wafer and the support substrate to form a beveled region and forming a first coating layer to be provided between the functional layer and the support substrate; a polishing step of polishing the functional layer wafer to form the functional layer; and a second coating layer formation step, after the polishing step, of forming a second coating layer that covers the functional layer, the side surface of the first coating layer, and the main surface of the support substrate on the functional layer wafer side in the beveled region.

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