Composite wafer and method for producing composite wafer

Abstract

Provided are a composite wafer having excellent heat resistance, and a method for producing the same. A composite wafer according to an embodiment of the present invention comprises a supporting substrate, an amorphous layer, and an SiO2-containing substrate in this order, wherein the amorphous layer is in contact with a first adjoining layer and a second adjoining layer, and includes an element contained in the first adjoining layer and the second adjoining layer. A composite wafer according to another embodiment of the present invention comprises a supporting substrate, an amorphous layer, and an SiO2-containing substrate having an OH group content of 100 ppm or less, in this order, wherein the amorphous layer is in contact with a first adjoining layer and a second adjoining layer, and includes an element contained in the first adjoining layer and the second adjoining layer. A method for producing a composite wafer according to an embodiment of the present invention includes directly bonding a supporting substrate to an SiO2-containing bulk body.

Description

COMPOSITE WAFER AND METHOD FOR MANUFACTURING COMPOSITE WAFER

[0001] The present invention relates to a composite wafer and a method for making the composite wafer.

[0002] Composite wafers, which are made up of stacked wafers containing different materials, can exhibit properties that cannot be achieved with single-layer wafers, and are therefore widely used in various fields such as semiconductors and electronic devices.

[0003] JP 2013-30617 A

[0004] On the other hand, depending on the material of the wafer, warping and breakage may occur due to heating, making stacking with other wafers difficult. This may limit the functional layers that can be formed on the support substrate. Therefore, there is a demand for composite wafers that can be stacked in a wider variety of combinations.

[0005] 1. The composite wafer of the present embodiment comprises a support substrate; an amorphous layer; and SiO ２ 2. Another embodiment of the present invention provides a composite wafer comprising a support substrate, an amorphous layer, and an SiO layer having an OH group content of 100 ppm or less, in this order, wherein the amorphous layer is in contact with a first adjacent layer and a second adjacent layer and contains the elements contained in the first adjacent layer and the second adjacent layer. ２ and a containing substrate; in this order, the amorphous layer is in contact with a first adjacent layer and a second adjacent layer and contains the elements contained in the first adjacent layer and the second adjacent layer. 3. In the composite wafer described in 1 or 2 above, the first adjacent layer is the support substrate, and the second adjacent layer is the SiO ２ 4. The composite wafer according to any one of the above items 1 to 3 may further include an intermediate layer, and at least one of the first adjacent layer and the second adjacent layer may be the intermediate layer. 5. In the composite wafer according to any one of the above items 1 to 4, the SiO ２The thickness of the containing substrate is 5 μm or more. 6. In the composite wafer described in any one of 1 to 5 above, the supporting substrate may be made of at least one material selected from the group consisting of silicon, indium phosphide, gallium nitride, gallium arsenide, aluminum nitride, and diamond. 7. In the composite wafer described in any one of 1, 3 to 6 above, the SiO ２ The containing substrate may be made of synthetic quartz glass, quartz glass, oxynitride glass, borosilicate glass, soda glass, or quartz. ２ The containing substrate may have a thinned surface on the surface opposite to the surface bonded to the support substrate. ２ A functional layer may be further laminated on the thinned surface of the containing substrate. 10. In the composite wafer described in 9 above, the functional layer may be composed of at least one selected from the group consisting of silicon nitride, niobium pentoxide, tantalum pentoxide, aluminum oxide, silicon, indium phosphide, gallium nitride, aluminum nitride, silicon carbide, gallium oxide, gallium arsenic, barium titanate, sapphire, lead zirconate titanate, lead lanthanum zirconate titanate, gallium phosphide, and potassium tantalate niobate. 11. In the composite wafer described in 2 above, the SiO ２ The containing substrate may be at least one selected from the group consisting of synthetic quartz glass, fused quartz glass, and sol-gel glass. ２ The containing substrate may have a thinned surface on the surface opposite to the surface bonded to the support substrate. ２A functional layer may be further laminated on the thinned surface of the containing substrate. 14. In the composite wafer described in 13 above, the functional layer may be composed of at least one selected from the group consisting of silicon nitride, niobium pentoxide, tantalum pentoxide, aluminum oxide, silicon, indium phosphide, gallium nitride, aluminum nitride, silicon carbide, gallium oxide, gallium arsenic, barium titanate, sapphire, lead zirconate titanate, lead lanthanum zirconate titanate, gallium phosphide, potassium tantalate niobate, lithium niobate, and lithium tantalate. 15. In the composite wafer described in any one of 1 to 14 above, the thermal expansion coefficient αs of the supporting substrate and the SiO ２ The thermal expansion coefficient αg of the containing substrate may satisfy the relationship 0.05≦αg / αs≦1.5. ２ The thermal expansion coefficient αg of the containing substrate and the thermal expansion coefficient αf of the functional layer may satisfy the relationship 0.5≦αf / αg≦10. 17. In another aspect of an embodiment of the present invention, there is provided a method for manufacturing a composite wafer. The method for manufacturing a composite wafer includes: forming a support substrate and a SiO ２ 18. In yet another aspect of the present invention, a method for manufacturing a composite wafer is provided. The method for manufacturing a composite wafer includes directly bonding a support substrate and a SiO ２ forming an intermediate layer on at least one of the containing bulk bodies, the intermediate layer formed on the supporting substrate, and SiO ２ Bulk body containing SiO ２ an intermediate layer formed on the inclusion bulk body and a supporting substrate; or an intermediate layer formed on the supporting substrate and the SiO ２ 19. The method for producing a composite wafer according to the above 17 or 18 includes directly bonding an SiO 3 layer bonded to a support substrate. ２ The bulk containing the SiO ２ 20. In the method for producing a composite wafer according to any one of items 17 to 19, the SiO ２The thickness of the inclusion bulk may be 100 μm or more. 21. The method for producing a composite wafer according to any one of items 17 to 20, further comprising the step of: ２ 22. The method for producing a composite wafer according to any one of items 17 to 21 above may further include forming a functional layer on the containing substrate. ２ The OH group content of the bulk material is 100 ppm or less.

[0006] According to an embodiment of the present invention, a composite wafer with excellent heat resistance and a method for manufacturing the composite wafer can be provided. The composite wafer of the embodiment of the present invention can be prevented from warping and breaking even when heated at a higher temperature. As a result, a composite wafer having a functional layer with higher performance can be provided. Furthermore, since the occurrence of warping is prevented, the functional layer can be formed by bonding. Furthermore, the functional layer and SiO ２ It is also possible to prevent a decrease in the bonding strength with the containing substrate.

[0007] 1A-1C are schematic cross-sectional views of a composite wafer according to an embodiment of the present invention, a composite wafer according to another embodiment of the present invention, and a composite wafer according to yet another embodiment of the present invention.

[0008] A. Overall Configuration of the Composite Wafer Fig. 1 is a schematic cross-sectional view of a composite wafer according to an embodiment of the present invention. The composite wafer 100 shown in the figure comprises a support substrate 20, an amorphous layer 30, and a SiO ２ and a containing substrate 10. In one embodiment, ２ The SiO-containing substrate 10 has an OH group content of 100 ppm or less. ２ The amorphous layer 30 is in contact with a first adjacent layer and a second adjacent layer. In the illustrated example, the first adjacent layer is the support substrate 20, and the second adjacent layer is SiO ２ In the illustrated example, the amorphous layer 30 is formed by a support substrate 20 and a SiO ２ The amorphous layer 30 is a layer formed by directly bonding the amorphous layer 30 to the supporting substrate 20, which is the first adjacent layer, and the SiO 2, which is the second adjacent layer. ２The amorphous layer 30 may further contain atomic species (typically argon, neon, krypton, helium, nitrogen, or xenon) that constitute the neutral atomic beam used in direct bonding. ２ The surface on the containing substrate 10 side is SiO ２ The amorphous layer 30 may form a clear interface with the containing substrate 10 (i.e., the second adjacent layer). Similarly, the surface of the amorphous layer 30 facing the support substrate 20 may form a clear interface with the support substrate 20 (i.e., the first adjacent layer). In one embodiment, SiO ２ The containing substrate 10 can be a layer having an amorphous structure such as quartz glass. In this embodiment, the second adjacent layer is also SiO ２ In the case of a substrate containing SiO ２ The interface between the containing substrate 10 and the amorphous layer 30 can be clearly distinguished. For example, when the composite wafer 100 on which the amorphous layer 30 is formed is observed at any appropriate magnification using a transmission electron microscope, the SiO ２ The interface on the containing substrate 10 side and the interface of the amorphous layer 30 on the support substrate 20 side can be confirmed.

[0009] The composite wafer 100 may further include an intermediate layer (not shown). The intermediate layer may be disposed in any suitable position. Specifically, the intermediate layer may be disposed between the support substrate 20 and the amorphous layer 30, or between the amorphous layer 30 and the SiO ２ An intermediate layer may be disposed between the containing substrate 10, between the support substrate 20 and the amorphous layer 30, and between the amorphous layer 30 and the SiO ２ An intermediate layer may be disposed between the containing substrate 10 and the supporting substrate 10. When the composite wafer includes an intermediate layer, the intermediate layer and the supporting substrate, the intermediate layer and the SiO ２The amorphous layer can be formed by directly bonding the containing substrate or the intermediate layer to the intermediate layer. In one embodiment, the first adjacent layer and / or the second adjacent layer is an intermediate layer. When the first adjacent layer and / or the second adjacent layer is an intermediate layer, the amorphous layer 30 can contain an element contained in the intermediate layer. For example, when the first adjacent layer is an intermediate layer and the second adjacent layer is a support substrate, the amorphous layer 30 can contain an element contained in the intermediate layer and an element contained in the support substrate. Also, when the first adjacent layer is SiO ２ If the second adjacent layer is an intermediate layer, the amorphous layer 30 may be SiO ２ The amorphous layer 30 may contain an element contained in the containing substrate and an element contained in the intermediate layer. Furthermore, when the first adjacent layer and the second adjacent layer are intermediate layers, the amorphous layer 30 may contain an element contained in the intermediate layer that is the first adjacent layer and an element contained in the intermediate layer that is the second adjacent layer. When the first adjacent layer and the second adjacent layer are intermediate layers, these intermediate layers may be formed of a material containing the same element or may be formed of a material containing different elements.

[0010] 2 is a schematic cross-sectional view of a composite wafer according to another embodiment of the present invention. The composite wafer 100 shown in the figure comprises a support substrate 20 and a SiO ２ The amorphous layer 30 is formed by directly bonding the containing substrate 10. In the illustrated example, the first adjacent layer is the support substrate 20, and the second adjacent layer is SiO ２ In the illustrated example, the substrate is a SiO ２ The surface of the containing substrate 10 opposite to the surface bonded to the support substrate 20 (i.e., SiO ２ The surface of the containing substrate 10 (the surface not bonded to the support substrate 20) has a thinned surface 50. The thinned surface 50 is formed by thinning the SiO ２ The raw material of the containing substrate (e.g., SiO ２ The thin layer can be produced by thinning a bulk material (containing bulk material) by polishing or the like.

[0011] 3 is a schematic cross-sectional view of a composite wafer according to yet another embodiment of the present invention. The composite wafer 100 shown in the figure includes a support substrate 20 and a SiO ２The amorphous layer 30 is formed by directly bonding the containing substrate 10. In the illustrated example, the first adjacent layer is the support substrate 20, and the second adjacent layer is SiO ２ The substrate contains SiO ２ The containing substrate 10 has a surface opposite to the surface bonded to the support substrate 20 (i.e., SiO ２ The surface of the containing substrate 10 (the surface not bonded to the support substrate 20) has a thinned surface 50. In this embodiment, SiO ２ The functional layer 40 is further laminated on the surface of the containing substrate 10 that is not bonded to the support substrate 20 (i.e., the thinned surface 50). The functional layer 40 is formed by any suitable method using SiO ２ It can be laminated on the containing substrate 10. For example, SiO ２ The functional layer 40 may be formed directly on the containing substrate 10, or the functional layer 40 may be formed on any suitable substrate by depositing it on SiO ２ The functional layer 40 may be transferred (reattached) to the containing substrate 10. ２ When the functional layer 40 is attached to the containing substrate 10, the SiO ２ The functional layer 40 and the containing substrate 10 may be laminated via any suitable bonding layer, or may be directly bonded. ２ When the functional layer 40 is directly bonded to the containing substrate 10, the SiO ２ An amorphous layer (not shown) may be formed between the containing substrate 10. When a functional layer is laminated by re-attaching, the base material used to form the functional layer may be peeled off or removed by any appropriate treatment such as polishing or smart cutting, or may be used as it is as a layer constituting the composite wafer.

[0012] As noted above, in one embodiment, the composite wafer of the present invention includes a first adjacent layer and a second adjacent layer (e.g., a support substrate 20 and a SiO ２ The amorphous layer 30 is formed by directly bonding the first adjacent layer and the second adjacent layer (for example, the support substrate 20 and the SiO ２ The composite wafer 100 is obtained by directly bonding the composite wafer 100 to a thinned surface 50, and the thinned surface 50 is made of SiO ２ The containing substrate 10 is SiO２ The raw material of the containing substrate (e.g., SiO ２ The composite wafer of the present invention is a layer formed by thinning a composite wafer (containing bulk body) by polishing or the like. Even when subjected to high temperatures, warping and breakage of the wafer can be suppressed. Therefore, a composite wafer with excellent heat resistance can be provided. Furthermore, because of the excellent heat resistance, it is possible to form and stack functional layers at higher temperatures. By forming the functional layer at high temperatures, impurities contained in the functional layer can be removed, and a functional layer with excellent crystallinity can be formed. Furthermore, the density of the functional layer can be improved. As a result, a composite wafer of higher quality can be provided.

[0013] The thermal expansion coefficient αs of the support substrate 20 and SiO ２ The ratio (αg / αs) of the thermal expansion coefficient αg of the containing substrate 10 preferably satisfies the relationship 0.05≦αg / αs≦1.5, more preferably 0.10≦αg / αs≦1.2, and even more preferably 0.15≦αg / αs≦1.0. If αg / αs is in the above range, a composite wafer with better heat resistance can be provided.

[0014] SiO ２ The ratio (αf / αg) of the thermal expansion coefficient αg of the containing substrate 10 to the thermal expansion coefficient αf of the functional layer 40 preferably satisfies the relationship 0.5≦αf / αg≦10. More preferably, it satisfies the relationship 0.6≦αf / αg≦9, and even more preferably, it satisfies the relationship 0.7≦αf / αg≦8. When αf / αg is within the above range, a composite wafer with better heat resistance can be provided.

[0015] The composite wafer 100 may further include any appropriate layers. The types, functions, number, combination, arrangement, etc. of such layers may be appropriately set depending on the purpose.

[0016] B. Support Substrate Any appropriate substrate can be used as the support substrate 20. The support substrate may be made of a single crystal or a polycrystalline material. It may also be made of a metal. Any appropriate material can be used as the material for the support substrate. Specifically, silicon (Si), indium phosphide (InP), gallium nitride (GaN), gallium arsenide (GaAs), aluminum nitride (AlN), diamond, silicon carbide (SiC), gallium oxide (GaO), sapphire (Al ２ O ３ Preferably, silicon (Si), indium phosphide (InP), gallium nitride (GaN), gallium arsenide (GaAs), aluminum nitride (AlN), and diamond can be used.

[0017] The thermal expansion coefficient αs of the support substrate 20 can be set to any appropriate value. ２ The thermal expansion coefficient of the support substrate 20 can be set so that the ratio (αg / αs) of the thermal expansion coefficient αg of the containing substrate 10 is within the above range. The thermal expansion coefficient αs of the support substrate is preferably 1.0 ppm / °C to 4.0 ppm / °C, more preferably 1.5 ppm / °C to 3.5 ppm / °C, and even more preferably 2.0 ppm / °C to 3.0 ppm / °C. For example, the thermal expansion coefficients of materials used to constitute the support substrate are as follows: silicon (2.6 ppm / °C), indium phosphide (4.5 ppm / °C), gallium nitride (5.6 ppm / °C), gallium arsenide (6.0 ppm / °C), aluminum nitride (4.6 ppm / °C), and diamond (0.7 ppm / °C). If the thermal expansion coefficient αs of the support substrate is within the above range, a composite wafer with superior heat resistance can be provided. The thermal expansion coefficient of the support substrate can be measured by any appropriate method. For example, it can be measured using a thermomechanical analyzer (TMA).

[0018] The density of the support substrate 20 can be set to any appropriate value. The density of the support substrate is preferably 1.5 g / cm ３ ~4.0 g / cm ３ and more preferably 2.0 g / cm３ ~3.5g / cm ３ and more preferably 2.2 g / cm ３ ~3.0 g / cm ３ For example, the thermal expansion coefficient of the material used to form the support substrate is as follows: silicon (2.3 g / cm ３ ), indium phosphide (4.79 g / cm ３ ), gallium nitride (6.15 g / cm ３ ), gallium arsenide (5.31 g / cm ３ ), aluminum nitride (3.26 g / cm ３ ), diamond (3.52 g / cm ３ If the density of the support substrate is within the above range, a composite wafer with better heat resistance can be provided. The density of the support substrate can be measured by any appropriate method. For example, it can be measured by density measurement using a pycnometer as specified in JIS Z 8807.

[0019] The thickness of the support substrate may be any appropriate thickness, for example, 100 μm to 1000 μm.

[0020] As described below, the composite wafer of the embodiment of the present invention includes a support substrate and a SiO ２ When the support substrate is silicon (Si), SiO 2 can be formed on the support substrate by thermal oxidation. ２ A layer (glass layer) containing SiO can be formed by thermal oxidation treatment. ２ When forming a layer containing SiO ２ Therefore, the layer may contain SiO in areas other than the specified area. ２ A layer containing SiO can be formed by thermal oxidation. ２ When forming a layer containing silicon dioxide, the layer is usually thermally oxidized at a temperature of 800 to 1200°C, so silicon dioxide and SiO ２ Therefore, the internal stress due to the difference in the thermal expansion coefficient between the layer containing SiO and the layer containing SiO other than the predetermined portion may remain. ２The performance may be significantly degraded due to the influence of residual stress caused by the removal of the layer containing SiO and / or the change in the layer structure. In addition, warping of the bonded wafer may also occur. Therefore, when forming a functional layer by bonding, ２ It may be difficult to bond the containing substrate and the functional layer. Furthermore, even if the functional layer is formed by bonding, the bonding strength may decrease due to residual internal stress, and peeling may occur at the bonded portion. The composite wafer of the embodiment of the present invention has a first adjacent layer and a second adjacent layer (for example, a support substrate and a SiO ２ The amorphous layer is formed by direct bonding between the support substrate and the SiO ２ The surface to which the containing substrate is not bonded is covered with SiO ２ In the bonded wafer according to the embodiment of the present invention, the support substrate and the SiO ２ The influence of residual stress during bonding with the containing substrate can be suppressed, which may make it possible to form a functional layer by bonding.

[0021] C. SiO ２ Containing substrate SiO ２ The containing substrate 10 is made of SiO ２ Any suitable substrate may be used, including SiO ２ The containing substrate may have a crystalline structure or an amorphous structure. ２ Even if the containing substrate has an amorphous structure, it can be clearly distinguished from an amorphous layer formed by direct bonding. ２Examples of materials constituting the containing substrate include synthetic quartz glass, quartz glass (natural quartz glass), oxynitride glass, borosilicate glass, soda-based glass, quartz, and chalcogenide glass. Synthetic quartz glass, quartz glass, oxynitride glass, borosilicate glass, soda-based glass, or quartz is preferred, and synthetic quartz glass or quartz glass is more preferred. In one embodiment, synthetic quartz glass with reduced OH groups may be used as the synthetic quartz glass. Using synthetic quartz glass with reduced OH groups can provide a composite wafer with low loss at high frequencies (e.g., 30 GHz or higher). In this embodiment, the OH groups contained in the synthetic quartz glass are, for example, 100 ppm or less.

[0022] As mentioned above, in one embodiment, SiO ２ The OH group content of the SiO-containing substrate is 100 ppm or less. ２ If the OH group content of the containing substrate is 100 ppm or less, SiO ２ The light absorption of the containing substrate can be suppressed. ２ The OH group content of the SiO-containing substrate is preferably 50 ppm or less, and more preferably 20 ppm or less. ２ The smaller the OH group content of the SiO-containing substrate, the more preferable, for example, 0.1 ppm or more. ２ The OH group content of the containing substrate can be measured by any suitable method.

[0023] SiO with an OH group content of 100 ppm or less ２ As the containing substrate, synthetic quartz glass, fused quartz glass, and sol-gel glass are preferably used. In the case of synthetic quartz glass, fused quartz glass, and sol-gel glass, SiO ２The content of OH groups contained in the containing substrate can be reduced. Synthetic quartz glass having an OH group content of 100 ppm or less can be produced by any appropriate method. For example, synthetic quartz glass having an OH group content of 100 ppm or less can be produced by casting. Casting can suppress the incorporation of OH groups and can also accommodate complex substrate shapes. Casting typically involves preparing a mold according to the shape of the substrate; pouring a slurry containing a raw material powder and a predetermined dispersant and dispersion medium into the mold; and solidifying the poured slurry in the mold and then firing it. When produced in this manner, silica or alumina is used as the raw material powder, so the incorporation of OH groups can be minimized. Casting can be performed, for example, by the procedure described in International Publication No. 2018 / 100775.

[0024] In addition, in the method for producing synthetic quartz glass, synthetic quartz glass may be produced using a material with a low content of OH groups. ４ (II) a direct process in which silicon tetrachloride (SiCl) is reacted with silicon dioxide (SiO 2 ) in an oxygen and hydrogen flame to produce silica particles, which are then melted at high temperatures to form glass; ４ ) in an oxygen and hydrogen flame to produce silica particles, which are deposited at low temperature and then sintered to form glass (the resulting SiO ２ (III) silicon tetrachloride (SiCl ４ ) by thermal oxidative decomposition or hydrolysis to produce porous silica, which is then sintered and vitrified by a plasma method (the resulting SiO ２ The direct method can produce quartz glass of very high purity. The soot method can produce quartz glass of even higher purity than the direct method. The electric melting method can further reduce the OH group content, improving the heat resistance of the resulting quartz glass. In addition, in the manufacturing process of synthetic quartz glass, OH groups may be reduced by reduction treatment using thionyl chloride or the like or by plasma firing.

[0025] The method for producing fused silica glass is an electric melting method in which quartz powder is melted by the heat of an electric furnace or plasma to produce quartz glass (the resulting SiO ２ The oxyhydrogen flame fusion method, in which quartz powder is melted using a high-temperature flame generated by the reaction of oxygen and hydrogen to form quartz glass, is one example of a method for producing sol-gel glass. Examples of methods for producing sol-gel glass include the sol-gel method, in which porous silica is made from silicon alkoxide and then sintered to form a glass (the resulting SiO ２ The amount of OH groups contained in the substrate is 1 ppm to 200 ppm.

[0026] SiO ２ The thickness of the containing substrate is preferably 0.1 μm or more, more preferably 2 μm to 15 μm, and even more preferably 5 μm to 11 μm. ２ If the thickness of the containing substrate is within the above range, a composite wafer with better heat resistance can be provided. Therefore, when a functional layer is further formed, the functional layer can be formed at a higher temperature. If the functional layer is formed at a high temperature, a functional layer with higher functionality (for example, higher density, higher purity) can be formed. The material constituting the functional layer is generally hard, and if the surface to be replaced is not flat, it may be difficult to closely adhere the surfaces to be bonded. The composite wafer of the embodiment of the present invention can further suppress warping. As a result, it may also be possible to form a functional layer by transfer (replacement). SiO ２ The substrate is SiO having an OH group content of 100 ppm or less. ２ In the case of a containing substrate, the thickness may be, for example, 0.1 μm to 15 μm, preferably 2 μm to 11 μm, and more preferably 4 μm to 10 μm.

[0027] SiO ２ The thermal expansion coefficient αg of the containing substrate 10 can be set to any appropriate value. ２ The ratio (αg / αs) of the thermal expansion coefficient αg of the containing substrate 10 satisfies the relationship 0.05≦αg / αs≦1.5, and SiO ２ The ratio of the thermal expansion coefficient αg of the containing substrate 10 to the thermal expansion coefficient αf of the functional layer 40 (αf / αg) satisfies the relationship 0.5≦αf / αg≦10.２ The thermal expansion coefficient of the containing substrate can be set. ２ The thermal expansion coefficient αg of the containing substrate is preferably 0.1 ppm / °C to 20 ppm / °C, more preferably 0.2 ppm / °C to 18 ppm / °C, and even more preferably 0.5 ppm / °C to 15 ppm / °C. ２ If the thermal expansion coefficient αg of the containing substrate is within the above range, a composite wafer having better heat resistance can be provided. ２ The thermal expansion coefficients of materials used to form the containing substrate are as follows: synthetic quartz glass (0.5 ppm / °C), quartz glass (natural quartz glass) (0.1 ppm / °C), borosilicate glass (5.2 ppm / °C), soda-based glass (soda-lime glass, 8.5 ppm / °C), quartz (z-axis: 7.48 ppm / °C, x-axis and y-axis: 13.71 ppm / °C), and chalcogenide glass (14 ppm / °C). ２ The thermal expansion coefficient of the containing substrate can be measured by any suitable method, for example, using a thermomechanical analyzer (TMA).

[0028] SiO ２ The density of the containing substrate 10 can be set to any suitable value. ２ The density of the containing substrate is preferably 1.5 g / cm ３ ~4.0 g / cm ３ and more preferably 2.0 g / cm ３ ~3.5g / cm ３ and more preferably 2.2 g / cm ３ ~3.0 g / cm ３ SiO ２ If the density of the containing substrate is within the above range, a composite wafer having better heat resistance can be provided. ２ The density of the material used to form the containing substrate is as follows: synthetic quartz glass (2.2 g / cm ３ ), quartz glass (natural quartz glass) (2.19 g / cm ３ ), borosilicate glass (2.3 g / cm ３ ), soda-lime glass (soda-lime glass, 2.5 g / cm３ ), crystal (2.65g / cm ３ ), chalcogenide glass (4.5 g / cm ３ ). SiO ２ The density of the inclusion substrate can be measured by any suitable method, for example, by density measurement using a pycnometer as specified in JIS Z 8807.

[0029] SiO ２ The containing substrate preferably has a thinned surface. For example, a 500 μm thick SiO ２ containing materials (e.g., SiO ２ The SiO2-containing bulk body is ground using a grinder and then polished with high precision by lapping or chemical mechanical polishing (CMP (Chemical Mechanical Polishing)) to obtain a thinned SiO2 film having a mirror-finished thinned surface with a thickness of 10 μm and a surface roughness Ra of 0.1 nm. ２ The composite wafer of the present invention may be obtained by, for example, combining a support substrate and SiO ２ This can be achieved by directly bonding the SiO2-containing bulk body. ２ The bulk containing material is thick and difficult to use as a composite wafer as it is. Therefore, it can be thinned to a predetermined thickness by any suitable method. Examples of the thinning method include polishing and smart cutting. In one embodiment, SiO ２ The SiO2-containing bulk body is polished to form a thin-layered surface. ２ A containing substrate can be obtained.

[0030] D. Amorphous Layer As described above, the amorphous layer 30 has an amorphous structure and is composed of elements constituting a first adjacent layer (e.g., the support substrate 20) and elements constituting a second adjacent layer (e.g., SiO ２ For example, the first adjacent layer is a support substrate made of silicon, and the second adjacent layer is made of SiO ２When the containing substrate is silica glass, the amorphous layer may contain the elements Si and oxygen. When the first adjacent layer and / or the second adjacent layer is an intermediate layer, the amorphous layer may contain the elements contained in the intermediate layer. For example, when the first adjacent layer is an intermediate layer and the second adjacent layer is a support substrate, the amorphous layer may contain the elements contained in the intermediate layer and the elements contained in the support substrate. Also, when the first adjacent layer is SiO ２ If the second adjacent layer is an intermediate layer, the amorphous layer may be SiO ２ The amorphous layer may contain an element contained in the containing substrate and an element contained in the intermediate layer. Furthermore, when the first adjacent layer and the second adjacent layer are intermediate layers, the amorphous layer may contain an element contained in the intermediate layer that is the first adjacent layer and an element contained in the intermediate layer that is the second adjacent layer. Furthermore, the amorphous layer may be formed by bonding the supporting substrate and SiO ２ The amorphous layer 30 may further contain iron and chromium resulting from the bonding process with the containing substrate. The amorphous layer 30 may further contain atomic species (typically argon, neon, krypton, helium, nitrogen, and xenon) that constitute the neutral atomic beam used for direct bonding. The content of such atomic species in the amorphous layer may be, for example, 1.5 atomic % to 2.5 atomic %.

[0031] The thickness of the amorphous layer may be, for example, from 0.1 nm to 100 nm, or for example, from 2 nm to 15 nm.

[0032] E. Intermediate Layer As described above, the composite wafer may further include an intermediate layer. The intermediate layer may be disposed in any suitable position. For example, the intermediate layer may be disposed between the support substrate and the amorphous layer, or between the amorphous layer and SiO ２ An intermediate layer may be disposed between the supporting substrate and the amorphous layer, and between the amorphous layer and the SiO ２ An intermediate layer may be disposed between the containing substrate and the insulating layer. The intermediate layer may be formed of any suitable material. Examples of materials for forming the intermediate layer include tantalum oxide (TaO). ２ O ５ ), niobium oxide (Nb ２ O ５ ), titanium oxide (TiO２ ), aluminum oxide (Al ２ O ３ ), hafnium oxide, silicon (for example, amorphous silicon), etc. Preferably, silicon such as amorphous silicon is used.

[0033] The thickness of the intermediate layer is, for example, 5 nm to 1 μm, and preferably 10 nm to 20 nm.

[0034] F. Functional Layer Any appropriate functional layer may be formed depending on the application and function of the composite wafer. For example, silicon nitride (SiN), niobium pentoxide (Nb ２ O ５ ), tantalum pentoxide (Ta ２ O ５ ), aluminum oxide (Al ２ O ３ ), silicon (Si), indium phosphide (InP), gallium nitride (GaN), aluminum nitride (AlN), silicon carbide (SiC), gallium oxide (Ga ２ O ３ ), gallium arsenide (GaAs), barium titanate (BaTiO ３ Examples of functional layers include those formed of lead zirconate titanate (PbZrTiO3 (PZT)), sapphire, lead lanthanum zirconate titanate (PLZT), gallium phosphide (GaP), and potassium tantalate niobate (KTN). ２ The SiO substrate has an OH group content of 100 ppm or less. ２ When a substrate containing silicon dioxide is used, the functional layer may be made of silicon nitride (SiN), niobium pentoxide (Nb ２ O ５ ), tantalum pentoxide (Ta ２ O ５ ), aluminum oxide (Al ２ O ３ ), silicon (Si), indium phosphide (InP), gallium nitride (GaN), aluminum nitride (AlN), silicon carbide (SiC), gallium oxide (Ga ２ O ３ ), gallium arsenide (GaAs), barium titanate (BaTiO ３Examples of functional layers include those formed of lead zirconate titanate (PbZrTiO3 (PZT)), sapphire, lead lanthanum zirconate titanate (PLZT), gallium phosphide (GaP), potassium tantalate niobate (KTN), lithium niobate (LN), and lithium tantalate (LT). As described above, the composite wafer of the present invention has excellent heat resistance. Therefore, the functional layer can be formed at a higher temperature. Formation at a higher temperature allows for the formation of a functional layer with higher functionality (e.g., higher density, higher purity). Furthermore, the occurrence of warpage in the composite wafer can be further suppressed. As a result, it may be possible to form the functional layer by transfer (re-bonding).

[0035] The composite wafer having a functional layer can be used for any suitable application depending on the functional layer. Specifically, the composite wafer having a functional layer formed of silicon nitride is suitable for use in optical devices. Specific examples include optical waveguides with a wide wavelength band from the visible to infrared range, optical comb devices using nonlinear optical effects, and erbium-doped optical waveguide optical amplifiers.

[0036] Composite wafers having functional layers made of niobium pentoxide, tantalum pentoxide, aluminum oxide, or sapphire are suitable for use in optical devices, such as optical waveguides with a wide wavelength range from the visible to the infrared.

[0037] Composite wafers having functional layers formed from silicon are suitable for use in electronic devices and optical devices. Examples of electronic devices include SOI wafers used in semiconductors such as CMOS (Complementary Metal-Oxide-Semiconductor) and memory. Examples of optical devices include silicon photonics, where the wafers are used in place of conventional thermally oxidized silicon in optical waveguide devices. Furthermore, optical modulators and photodiodes may be formed in silicon to form optical integrated circuits.

[0038] The composite wafer having a functional layer formed of indium phosphide or gallium arsenide is suitable for use in electronic devices and optical devices. ２ The substrate containing the silicon dioxide may be used as an insulating layer for a high-speed transistor. In optical devices, the silicon dioxide may be used as an insulating layer or a low refractive index layer. ２ Examples of the optical integrated circuit include an optical integrated circuit using a containing substrate, more specifically an optical integrated circuit in which an optical modulator, a laser, or a photodiode is formed.

[0039] The composite wafer having a functional layer formed of gallium nitride and aluminum nitride is suitable for use in electronic devices and optical devices. Specifically, in electronic devices, the SiO of the composite wafer is used as an insulating layer for transistors capable of high-speed operation. ２ Substrates containing SiO 2 can be used for optical devices, specifically composite wafers. ２ Examples of such an optical integrated circuit include an optical integrated circuit using a substrate containing the compound as an insulating layer or a low refractive index layer, and more specifically, an optical integrated circuit in which an optical modulator, a laser, or a photodiode is formed.

[0040] The composite wafer having a functional layer formed of silicon carbide is suitable for use in electronic devices and optical devices. For example, in electronic devices, a SiO 2 layer is applied to the composite wafer as an insulating layer for transistors capable of controlling high power or high-speed operation. ２ Substrates containing, for example, SiO2 of a composite wafer can be used for optical devices. ２ Examples include an optical waveguide with a wide wavelength band from visible light to infrared light, which uses a substrate containing the compound as a low refractive index layer, and an optical comb device that uses nonlinear optical effects.

[0041] The composite wafer having a functional layer formed of gallium oxide is suitable for use in electronic devices. ２ Examples of such transistors include transistors that use a substrate containing silicon as an insulating layer and are capable of controlling large amounts of power or operating at high speeds.

[0042] A composite wafer having a functional layer formed of barium titanate, lead zirconate titanate, lead lanthanum zirconate titanate, or potassium tantalate niobate is suitable for use in optical devices. ２ Examples of the material include an optical modulator and an optical scanner element that can be operated at a low driving voltage and that use a substrate containing the material as a low refractive index layer.

[0043] The composite wafer having a functional layer formed of gallium phosphide is suitable for use in optical devices. ２ Examples of such devices include devices that use the inclusion substrate as a low refractive index layer to generate mid-infrared or terahertz waves.

[0044] SiO ２ The SiO substrate has an OH group content of 100 ppm or less. ２ When a substrate containing lithium niobate or lithium tantalate is used, the composite wafer having a functional layer formed thereon is suitable for use as an optical device. For example, the SiO ２ Examples of the device include an optical modulator and an optical scanner element that can operate at a low driving voltage by utilizing the electro-optic effect, and a wavelength conversion device that utilizes the nonlinear optical effect, using a substrate containing the material as a low refractive index layer.

[0045] The functional layer is preferably made of the above-mentioned SiO ２ The functional layer can be laminated on the thinned surface of the containing substrate. The functional layer can be formed by any suitable method. ２ The functional layer may be formed directly on the thinned surface of the containing substrate, or may be formed on any suitable substrate by heating the functional layer to a thickness of SiO ２ The functional layer may be transferred (replaced) on the thinned surface of the containing substrate. ２ The containing substrate and the functional layer may be directly bonded to each other, or may be laminated via any suitable bonding layer.

[0046] The thermal expansion coefficient αf of the functional layer 40 can be set to any appropriate value. ２The thermal expansion coefficient of the functional layer can be set so that the ratio (αf / αg) to the thermal expansion coefficient αg of the containing substrate 10 satisfies the relationship 0.5≦αf / αg≦10. The thermal expansion coefficient αf of the functional layer 40 is preferably 1 ppm / °C to 17 ppm / °C, more preferably 1 ppm / °C to 10 ppm / °C, even more preferably 1.5 ppm / °C to 8 ppm / °C, and particularly preferably 2 ppm / °C to 5 ppm / °C. If the thermal expansion coefficient αf of the functional layer is within the above range, a composite wafer with better heat resistance can be provided. For example, the thermal expansion coefficients of materials used to form the functional layers are as follows: silicon nitride (3 ppm / °C to 3.5 ppm / °C), niobium pentoxide (5.8 ppm / °C), tantalum pentoxide (5 ppm / °C), aluminum oxide (5.3 ppm / °C), silicon (2.6 ppm / °C), indium phosphide (4.5 ppm / °C), gallium nitride (5.6 ppm / °C), aluminum nitride (4.6 ppm / °C), silicon carbide (4.0 ppm / °C), and tantalum pentoxide (5.8 ppm / °C). Gallium (2.0 ppm / °C), gallium arsenide (6.0 ppm / °C), barium titanate (5.0 ppm / °C), sapphire (5.5 ppm / °C), lead zirconate titanate (3.4 ppm / °C), lead lanthanum zirconate titanate (5.4 ppm / °C), potassium tantalate niobate (3 ppm / °C), gallium phosphide (5.3 ppm / °C), lithium niobate (5.0 ppm / °C to 16.0 ppm / °C), and lithium tantalate (4.0 ppm / °C to 16.0 ppm / °C). The thermal expansion coefficient of the functional layer can be measured by any suitable method. For example, it can be measured using a thermomechanical analyzer (TMA).

[0047] The density of the functional layer 40 can be set to any appropriate value. The density of the functional layer is preferably 1.5 g / cm ３ ~7.5g / cm ３ and preferably 1.5 g / cm ３ ~6.0 g / cm ３ and more preferably 2.0 g / cm ３ ~5.0 g / cm ３ and more preferably 2.5 g / cm ３ ~4.0 g / cm ３As described above, the bonded wafer according to the embodiment of the present invention has excellent heat resistance, and therefore a functional layer with higher density can be formed. For example, the density of the material used to form the functional layer is as follows: silicon nitride (3.2 g / cm ３ ), niobium pentoxide (4.47 g / cm ３ ), tantalum pentoxide (8.18 g / cm ３ ), aluminum oxide (3.9 g / cm ３ ), silicon (2.3 g / cm ３ ), indium phosphide (4.79 g / cm ３ ), gallium nitride (6.15 g / cm ３ ), aluminum nitride (3.26 g / cm ３ ), silicon carbide (3.2 g / cm ３ ), gallium oxide (α: 6.4 g / cm ３ , β: 5.9 g / cm ３ ), gallium arsenide (5.31 g / cm ３ ), barium titanate (6.0 g / cm ３ ), sapphire (4.0 g / cm ３ ), lead zirconate titanate (7.5 g / cm ３ ), lead lanthanum zirconate titanate (7.6 g / cm ３ ), or potassium tantalate niobate (6.4 g / cm ３ ) gallium phosphide (4.13 g / cm ３ ), lithium niobate (4.65 g / cm ３ ), and lithium tantalate (7.46 g / cm ３ The density of the functional layer can be measured by any suitable method, for example, by density measurement using a pycnometer as specified in JIS Z 8807.

[0048] The thickness of the functional layer can be set to any appropriate thickness. The thickness of the functional layer can be set to any appropriate thickness. The thickness of the functional layer is preferably 0.1 μm to 10 μm, more preferably 0.3 μm to 2 μm, and even more preferably 0.4 μm to 1 μm. If the thickness of the functional layer is within the above range, the effects achieved by providing the functional layer can be sufficiently obtained.

[0049] G. Manufacturing Method In another aspect of the present invention, a method for manufacturing a composite wafer can be provided. The method for manufacturing a composite wafer of the present invention includes: forming a support substrate and a SiO ２ The method includes directly bonding the supporting substrate and the SiO ２ By directly bonding the supporting substrate and the SiO -containing bulk body, a composite wafer with better heat resistance can be obtained. ２ When the supporting substrate and the SiO ２ In the composite wafer obtained by this manufacturing method, the first adjacent layer is a support substrate, and the second adjacent layer is a SiO 2 layer. ２ As described below, the substrate may be a SiO ２ The bulk material containing SiO is thinned by the thinning treatment. ２ It can function as a containing substrate.

[0050] SiO ２ The bulk material containing the silicon dioxide may be any suitable bulk material that is obtained by crystal growth and / or synthesis, rather than by film formation. ２ The bulk of the material that constitutes the containing substrate can be used. ２ The thickness of the containing bulk body can be set to any appropriate thickness. ２ The thickness of the inclusion bulk body is preferably 100 μm or more, more preferably 200 μm to 1000 μm, and even more preferably 250 μm to 500 μm. ２ When the thickness of the inclusion bulk material is within the above range, it can be bonded well to the support substrate by direct bonding, and the heat resistance of the resulting composite wafer can be improved.

[0051] SiO ２ The bulk body containing the SiO 2 can be produced by any suitable method, such as a direct synthesis method, a plasma synthesis method, a soot synthesis method, a sol-gel synthesis method, an oxyhydrogen flame fusion method, or an electric fusion method. Depending on the method for producing the bulk body, the raw materials may vary, thereby resulting in the formation of SiO 2 . ２The amount of metal impurities and the amount of OH groups contained in the bulk material may change, and various properties may also change. For example, by using a synthesis method, the amount of metal impurities and the amount of OH groups can be relatively reduced. Specific methods are as described above.

[0052] The above-mentioned materials can be used as the support substrate. ２ The direct bonding with the containing bulk body is carried out by any suitable method. For example, a surface activation method, a plasma method, an atomic diffusion method, etc. may be mentioned. Alternatively, the direct bonding may be carried out by the following method: In a high vacuum chamber (for example, 1×10 －６ At a pressure of about Pa, the support substrate and SiO ２ A neutralization beam is irradiated onto each bonding surface of the bulk material containing the silicon dioxide. This activates each bonding surface. Next, the activated bonding surfaces are brought into contact with each other in a vacuum atmosphere and bonded at room temperature. The load during this bonding can be, for example, 100 N to 20,000 N. In one embodiment, when performing surface activation using a neutralization beam, an inert gas is introduced into a chamber, and a high voltage is applied from a DC power supply to an electrode placed in the chamber. With this configuration, an electric field generated between the electrode (positive electrode) and the chamber (negative electrode) causes electrons to move, generating a beam of atoms and ions from the inert gas. Of the beams that reach the grid, the ion beam is neutralized by the grid, and a beam of neutral atoms is emitted from the fast atom beam source. The atomic species that make up the beam are typically argon, neon, krypton, helium, nitrogen, and xenon. The voltage during activation by beam irradiation is, for example, 0.5 kV to 2.0 kV, and the current is, for example, 50 mA to 200 mA. As described above, atoms contained in the neutral atomic beam can be included in the amorphous layer formed by direct bonding.

[0053] In another embodiment of the present invention, a method for manufacturing a composite wafer includes: a support substrate; and a SiO ２ Forming an intermediate layer on at least one of the containing bulk bodies, the intermediate layer formed on the support substrate, and SiO ２ Bulk body containing SiO ２ an intermediate layer formed on the inclusion bulk body and a supporting substrate; or an intermediate layer formed on the supporting substrate and a SiO ２Specifically, when the intermediate layer is formed on the support substrate, the intermediate layer formed on the support substrate and the SiO ２ In this case, the element contained in the intermediate layer formed on the support substrate and the SiO ２ In the composite wafer obtained by this manufacturing method, the first adjacent layer is an intermediate layer formed on the support substrate, and the second adjacent layer is an SiO ２ As described below, the substrate may be a SiO ２ The SiO-containing bulk body can function as a SiO2-containing substrate by being thinned. ２ When an intermediate layer is formed on the containing bulk body, SiO ２ The intermediate layer formed on the containing bulk body is directly bonded to the support substrate. ２ An amorphous layer containing an element contained in the intermediate layer formed in the inclusion bulk body and an element contained in the support substrate can be formed. In the composite wafer obtained by this manufacturing method, the first adjacent layer is the support substrate, and the second adjacent layer is SiO ２ The intermediate layer may be formed on the supporting substrate and the SiO ２ When an intermediate layer is formed on the containing bulk body, the intermediate layer formed on the support substrate and SiO ２ The intermediate layer formed on the containing bulk body is directly bonded. ２ An amorphous layer containing the element contained in the intermediate layer formed on the inclusion bulk body and the element contained in the intermediate layer formed on the support substrate can be formed. In the composite wafer obtained by this manufacturing method, the first adjacent layer is the intermediate layer formed on the support substrate, and the second adjacent layer is SiO ２ It may be an intermediate layer formed on the containing bulk body. ２ an intermediate layer formed on the inclusion bulk body and a support substrate; an intermediate layer formed on the support substrate and a SiO ２ or an intermediate layer formed on a support substrate and a SiO ２ By directly bonding the intermediate layer formed on the containing bulk body, a composite wafer having better heat resistance can be obtained.

[0054] The intermediate layer can be formed by any appropriate method. Examples include physical vapor deposition such as sputtering, vacuum deposition, and ion beam assisted deposition (IAD), chemical vapor deposition, and atomic layer deposition (ALD). The intermediate layer may be formed by heating the substrate, or may be formed without heating the substrate. When the substrate is heated, the heating temperature can be, for example, 100°C to 300°C, preferably 120°C to 250°C, and more preferably 140°C to 200°C. When the intermediate layer is formed between the support substrate and the amorphous layer, the SiO ２ An intermediate layer may be formed on the surface to be bonded to the bulk material, and then the direct bonding may be performed. ２ When an intermediate layer is formed between the containing substrate, SiO ２ An intermediate layer may be formed on the surface of the bulk containing material to be bonded to the support substrate, and then the direct bonding may be performed. As described above, the intermediate layer may be formed of any appropriate material. Specifically, tantalum oxide (Ta ２ O ５ ), niobium oxide (Nb ２ O ５ ), titanium oxide (TiO ２ ), aluminum oxide (Al ２ O ３ ), hafnium oxide, silicon (for example, amorphous silicon), etc. The thickness of the intermediate layer is, for example, 5 nm to 1 μm, and preferably 10 nm to 200 nm.

[0055] An intermediate layer formed on a support substrate, and SiO ２ Direct bonding with the containing bulk body: SiO ２ Direct bonding between an intermediate layer formed on the containing bulk body and a supporting substrate; ２ The direct bonding to the intermediate layer formed on the inclusion bulk body can be carried out by any appropriate method, specifically the methods described above.

[0056] SiO directly bonded to the support substrate ２ The containing bulk body is preferably thinned, and SiO ２ The containing substrate can be fabricated. Typically, the bulk thickness is SiO 2 which can be formed into a composite wafer. ２The thickness is thicker than the thickness of the containing substrate. By thinning, the thickness can be adjusted to a thickness suitable for use as a composite wafer. Thinning can be performed by any suitable method. For example, thinning can be performed by using any suitable abrasive to remove SiO ２ The surface of the bulk body that is not directly bonded to the support substrate is polished and thinned to a predetermined thickness, thereby forming a SiO ２ A silicon-containing substrate can be produced. It can also be thinned by Smart Cut. Smart Cut is a well-known method for thinning silicon substrates. Specifically, hydrogen ions are implanted into silicon to form a minute void layer at a depth of 1 μm or less from the surface. Then, the silicon is heat-treated at 100° C. to 500° C., which grows the voids and cleaves the silicon, resulting in thinning.

[0057] The method for manufacturing a composite wafer according to an embodiment of the present invention preferably comprises the steps of: ２ The method further includes laminating a functional layer on the containing substrate. In the above process, the directly bonded laminate (composite wafer) has excellent heat resistance. More specifically, even when subjected to high-temperature processing, warping and breakage of the composite wafer can be suppressed. Therefore, when the functional layer is provided by direct film formation, the functional layer can be formed at a higher temperature, for example, 400°C or higher. As a result, a functional layer with higher functionality (for example, higher density and higher purity) can be formed. When the functional layer is provided by direct film formation, the film formation temperature is preferably 850°C or lower, more preferably 800°C or lower, and particularly preferably 700°C or lower. For example, when forming a functional layer using silicon nitride, SiO ２ The functional layer can be formed by directly depositing a film on the containing substrate. In this embodiment, the functional layer formed of silicon nitride can be formed at, for example, 400 to 800°C. In addition, the functional layer can be formed by depositing a film directly on the containing substrate. ２ A functional layer can be formed on the containing substrate.

[0058] In another embodiment, the functional layer is formed on any suitable substrate by coating the functional layer with SiO ２The functional layer is generally a hard layer, and when warping occurs on the bonding surface of the composite wafer, the bonding surface of the functional layer and the SiO ２ Therefore, even if the laminate is directly bonded or laminated via any suitable bonding layer, it may be difficult to achieve sufficient adhesion with the bonding surface of the SiO ２ The functional layer may peel off from the containing substrate, and sufficient durability may not be obtained. ２ The bonding surface of the containing substrate can be sufficiently adhered to the bonding surface. Furthermore, when a thinned surface is formed by polishing or the like, the smoothness of the thinned surface is also improved, and adhesion can be further improved. Furthermore, a composite wafer in which each layer is more closely adhered can be obtained by direct bonding or stacking via any appropriate bonding layer. In this embodiment, the substrate used to form the functional layer is SiO ２ The layer may be peeled off and removed after being attached to the containing substrate, or may be removed by any suitable treatment such as polishing, or may be used as it is as a layer constituting the composite wafer.

[0059] The direct bonding method is the above-mentioned method. ２ When laminating the containing substrate and the functional layer, any suitable bonding layer may be interposed depending on the material of the functional layer. For example, tantalum oxide (Ta ２ O ５ ), niobium oxide (Nb ２ O ５ ), titanium oxide (TiO ２ ), aluminum oxide (Al ２ O ３ ), hafnium oxide, silicon (for example, amorphous silicon), etc. The thickness of the bonding layer is, for example, 5 nm to 1 μm, and preferably 10 nm to 200 nm.

[0060] The bonding layer can be formed by any suitable method. For example, it can be formed by physical vapor deposition such as sputtering, vacuum deposition, or ion beam assisted deposition (IAD), chemical vapor deposition, or atomic layer deposition (ALD). The bonding layer can be formed, for example, at a temperature of 100°C to 300°C, preferably 120°C to 250°C, and more preferably 140°C to 200°C. The bonding layer may also be formed at room temperature. Lamination of functional layers by re-attachment is suitable when semiconductors such as Si and SiC, or ceramics such as BTO and PZT, are used as materials for forming the functional layers.

[0061] The present invention will be specifically explained below with reference to examples, but the present invention is not limited to these examples.

[0062] Example 1 1. Preparation of a Composite Wafer A composite wafer was prepared by bonding a silicon wafer, a synthetic quartz glass wafer (OH group concentration: 15 ppm), and an X-plate LN wafer. Specifically, the surfaces of a silicon wafer (4 inches, resistivity 10 kΩcm or more, thickness 525 μm) and a synthetic quartz glass bulk (4 inches, thickness 500 μm, OH content 15 ppm) were first polished to a high flatness to an arithmetic mean surface roughness Ra of 0.2 nm. Next, the polished surfaces were bonded using a wafer surface activation method. Specifically, the silicon wafer and the synthetic quartz glass bulk were placed in a vacuum chamber, and in a vacuum of the 10 Pa-6 Pa range, the bonding surfaces of the silicon wafer and the synthetic quartz glass bulk were irradiated with a high-speed Ar neutral atom beam (accelerating voltage 1 kV, Ar flow rate 60 sccm) for 70 seconds. After irradiation, the silicon wafer was left to cool for 10 minutes, and the beam-irradiated surface of the silicon wafer was brought into contact with the beam-irradiated surface of the synthetic quartz glass bulk body, and a pressure of 4.90 kN was applied for 2 minutes to bond the silicon wafer and the synthetic quartz glass bulk body. The synthetic quartz glass bulk body was then ground by precision polishing to a thickness of 2 μm, and a synthetic quartz glass wafer (SiO ２(containing substrate). Separately, an X-plate LN wafer was subjected to high-flatness polishing so that the arithmetic mean surface roughness Ra of the surface was 0.2 nm. Next, the synthetic quartz glass wafer and the LN wafer of the wafer obtained by bonding the silicon wafer and synthetic quartz glass wafer were bonded together by plasma activation. Thereafter, the LN wafer side of the bonded LN wafer / synthetic quartz glass wafer / silicon wafer stack was subjected to precision polishing to a thickness of 600 nm, thereby obtaining a composite wafer. An amorphous layer was formed between the silicon wafer and the synthetic quartz glass wafer.

[0063] 2. Optical Waveguide Formation A 300 nm diamond-like carbon (DLC) film was formed on the LN wafer side of a composite wafer of an LN wafer / synthetic quartz glass wafer / silicon wafer using plasma-enhanced chemical vapor deposition (PECVD). Next, a resist was applied, and a resist pattern for forming an optical waveguide was formed by photolithography. The resist pattern was then used as a mask to perform reactive ion etching in oxygen plasma, etching the DLC. Furthermore, the DLC was used as a hard mask to perform dry etching in Ar gas, etching the LN wafer by 400 nm to form a ridge-type optical waveguide. At this time, the width of the ridge waveguide at the surface was 1.5 μm, and the remaining thickness of the LN wafer at the etched portion was 200 nm. Three types of optical waveguides were formed: lengths of 10 mm, 20 mm, and 30 mm. The remaining DLC ​​pattern was then removed by etching to complete the process.

[0064] 3. Optical Evaluation The composite wafer with the optical waveguide formed was diced into optical waveguide elements with lengths of 10 mm, 20 mm, and 30 mm, and both end faces of each optical waveguide element were polished. The optical waveguide elements were coupled to the optical waveguide element using a bulb-tipped fiber, and the optical insertion loss of each was measured. Specifically, light was introduced into the optical waveguide element through the input bulb-tipped fiber coupled to the optical fiber, and the amount of light output through the output bulb-tipped fiber was measured with a photodetector to calculate the propagation loss. Evaluation was performed using lasers with wavelengths of 1.31 μm, 1.48 μm, 1.55 μm, and 1.61 μm. Length dependency was evaluated using optical insertion loss data for different element lengths, and the optical propagation loss was calculated from the slope. As a result of the measurement, the optical propagation loss was 0.05 dB / cm to 0.1 dB / cm at the above wavelengths.

[0065] (Comparative Example) 1. Composite wafer formation Silicon wafer, sputtered SiO ２ A composite wafer was produced by bonding a silicon wafer (4 inches, resistivity 10 kΩcm or more, thickness 525 μm) to a silicon wafer in the same manner as in the example, and polishing was performed to achieve a high flatness, with the arithmetic mean surface roughness Ra of the surface being 0.2 nm. Next, a SiO 2 film was applied to the surface of the silicon wafer using a sputtering device. ２ Then, a SiO film was formed to a thickness of 2 μm. ２ The film surface was subjected to precision polishing. Separately, an X-plate LN wafer was subjected to high flatness polishing so that the arithmetic mean surface roughness Ra of the surface was 0.2 nm. ２ SiO of the silicon wafer on which the film was formed ２ The membrane side and the LN wafer were bonded by plasma activation. ２ The LN wafer side of the membrane / silicon wafer laminate was precision polished to a thickness of 600 nm to obtain a composite wafer.

[0066] Thereafter, an optical waveguide pattern was formed on the resulting composite wafer in the same manner as in Example 1. The optical propagation loss was then calculated in the same manner as in Example 1. As a result, the optical propagation loss was 0.3 dB / cm to 0.4 dB / cm at wavelengths of 1.31 μm, 1.48 μm, 1.55 μm, and 1.61 μm.

[0067] The composite wafer according to the embodiment of the present invention can be suitably used for semiconductors, electronic devices, optical devices, and the like.

[0068] 10 SiO ２ 1. Containing substrate 20 Support substrate 30 Amorphous layer 40 Functional layer 50 Thinned surface 100 Composite wafer

Claims

1. A supporting substrate; an amorphous layer; and SiO ２ a containing substrate; and a first adjacent layer; the amorphous layer in contact with a first adjacent layer and a second adjacent layer, the amorphous layer comprising an element contained in the first adjacent layer and the second adjacent layer.

2. A support substrate; an amorphous layer; and a SiO layer having an OH group content of 100 ppm or less. ２ a containing substrate; and a first adjacent layer; the amorphous layer in contact with a first adjacent layer and a second adjacent layer, the amorphous layer comprising an element contained in the first adjacent layer and the second adjacent layer.

3. The first adjacent layer is the support substrate, and the second adjacent layer is the SiO ２ 3. The composite wafer of claim 1 or 2, which is a containing substrate.

4. The composite wafer of claim 1 or 2, further comprising an intermediate layer, at least one of said first adjacent layer and said second adjacent layer being said intermediate layer.

5. The SiO ２ 3. The composite wafer according to claim 1 or 2, wherein the thickness of the containing substrate is 5 μm or more.

6. The composite wafer according to claim 1 or 2, wherein the support substrate is at least one selected from the group consisting of silicon, indium phosphide, gallium nitride, gallium arsenide, aluminum nitride, and diamond.

7. The SiO ２ 2. The composite wafer of claim 1, wherein the containing substrate is comprised of synthetic fused silica, fused silica, oxynitride glass, borosilicate glass, soda-lime glass, or quartz.

8. The SiO ２ The composite wafer according to claim 1 , wherein the containing substrate has a thinned surface on the surface opposite to the surface bonded to the support substrate.

9. The SiO ２ The composite wafer according to claim 8 , further comprising a functional layer laminated on the thinned surface of the containing substrate.

10. The composite wafer of claim 9, wherein the functional layer is comprised of at least one selected from the group consisting of silicon nitride, niobium pentoxide, tantalum pentoxide, aluminum oxide, silicon, indium phosphide, gallium nitride, aluminum nitride, silicon carbide, gallium oxide, gallium arsenide, barium titanate, sapphire, lead zirconate titanate, lead lanthanum zirconate titanate, gallium phosphide, and potassium tantalate niobate.

11. The SiO ２ 3. The composite wafer according to claim 2, wherein the containing substrate is at least one selected from the group consisting of synthetic quartz glass, fused quartz glass, and sol-gel glass.

12. The SiO ２ The composite wafer according to claim 2 , wherein the containing substrate has a thinned surface on the surface opposite to the surface bonded to the support substrate.

13. The SiO ２ The composite wafer according to claim 12 , further comprising a functional layer laminated on the thinned surface of the containing substrate.

14. The composite wafer of claim 13, wherein the functional layer is comprised of at least one selected from the group consisting of silicon nitride, niobium pentoxide, tantalum pentoxide, aluminum oxide, silicon, indium phosphide, gallium nitride, aluminum nitride, silicon carbide, gallium oxide, gallium arsenide, barium titanate, sapphire, lead zirconate titanate, lead lanthanum zirconate titanate, gallium phosphide, and potassium tantalate niobate, lithium niobate, and lithium tantalate.

15. The thermal expansion coefficient αs of the support substrate and the SiO ２ The composite wafer according to claim 1 or 2, wherein the thermal expansion coefficient αg of the containing substrate satisfies the relationship: 0.05≦αg / αs≦1.

5.

16. The SiO ２ The composite wafer according to claim 10 or 14, wherein the thermal expansion coefficient αg of the containing substrate and the thermal expansion coefficient αf of the functional layer satisfy the relationship 0.5≦αf / αg≦10.

17. Support substrate and SiO ２ A method for producing a composite wafer, comprising directly bonding a containing bulk body to the composite wafer.

18. Support substrate and SiO ２ forming an intermediate layer on at least one of the inclusion bulk bodies; ２ Containing bulk body; the SiO ２ An intermediate layer formed on the inclusion bulk body and a supporting substrate; or an intermediate layer formed on the supporting substrate and the SiO ２ An intermediate layer formed on the containing bulk body; and a method for producing a composite wafer, comprising directly bonding the containing bulk body and the intermediate layer to each other.

19. SiO bonded to a supporting substrate ２ The bulk containing the SiO ２ 19. A method for producing a composite wafer according to claim 17 or 18, further comprising preparing a containing substrate.

20. The SiO ２ The method for producing a composite wafer according to claim 17 or 18, wherein the thickness of the inclusion bulk is 100 μm or more.

21. The SiO ２ 20. The method of claim 17, further comprising forming a functional layer on the containing substrate.

22. The SiO ２ The method for producing a composite wafer according to claim 21, wherein the OH group content of the containing bulk body is 100 ppm or less.

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