Joined body, device, and method for manufacturing joined body

Abstract

Disclosed is a joined body 1 which comprises a piezoelectric layer 11a that is formed of a piezoelectric material, a dielectric layer 12 that is disposed under the piezoelectric layer 11a, and a support substrate 13 that is joined to the piezoelectric layer 11a with the dielectric layer 12 being sandwiched therebetween, wherein: the dielectric layer 12 includes a first silicon oxide layer 12a that is in contact with the piezoelectric layer 11a, and a second silicon oxide layer 12b that is positioned closer to the support substrate 13 than the first silicon oxide layer 12a; and the content of argon contained in the first silicon oxide layer 12a is higher than the content of argon contained in the second silicon oxide layer 12b. Consequently, the present invention provides: a joined body which is not susceptible to separation of a piezoelectric substrate even if the piezoelectric substrate is processed and the like after a support substrate and the piezoelectric substrate are bonded with each other; and a method for manufacturing the joined body.

Description

Bonded body, device, and method for manufacturing the bonded body

[0001] The present invention relates to a bonded structure, a device, and a method for manufacturing the bonded structure.

[0002] In order to realize high-performance semiconductor devices, a structure in which a support substrate and a piezoelectric material substrate are bonded together is used. In recent years, in order to realize even higher performance devices, a structure in which a silicon oxide layer is provided as an intermediate layer between the support substrate and the piezoelectric material substrate has been proposed.

[0003] Patent Document 1 discloses a method for manufacturing a composite wafer. This method for manufacturing a composite wafer includes the steps of implanting hydrogen atomic ions or hydrogen molecular ions from the surface to form an ion-implanted layer inside the oxide single crystal wafer, performing a surface activation treatment on at least one of the ion-implanted surface of the oxide single crystal wafer and the surface of a support wafer, and bonding the ion-implanted surface of the oxide single crystal wafer and the surface of the support wafer to obtain a bonded body. This method for manufacturing a composite wafer also includes the steps of heat-treating the bonded body at a temperature of 90°C or higher at which cracks do not occur, and irradiating the heat-treated bonded body with visible light to obtain an oxide single crystal thin film that is peeled along the ion-implanted layer and transferred onto the support wafer.

[0004] Patent Document 2 discloses that a bonded structure includes a support substrate, a piezoelectric material substrate made of a material selected from the group consisting of lithium niobate, lithium tantalate, and lithium niobate-lithium tantalate, and a bonding layer bonding the support substrate and the piezoelectric material substrate. The bonding layer is made of silicon oxide. When the bonding layer is divided into a bonding portion on the piezoelectric material substrate side and a bonding portion on the support substrate side, the nitrogen concentration in the bonding portion on the piezoelectric material substrate side is higher than the nitrogen concentration in the bonding portion on the support substrate side.

[0005] JP 2016-225537 A International Publication No. 2019 / 130895

[0006] In conventional methods, the silicon oxide layer provided on the support substrate is formed, for example, by thermal oxidation. However, after bonding a silicon substrate having this silicon oxide layer to a piezoelectric material substrate using conventional techniques, processing or heat treatment of the piezoelectric substrate can cause peeling of the piezoelectric substrate. The present invention aims to provide a bonded structure and a method for manufacturing the bonded structure that are less likely to cause peeling of the piezoelectric substrate even when processing the piezoelectric substrate after bonding the support substrate and the piezoelectric substrate. Another aim of the present invention is to provide a device using this bonded structure.

[0007] In order to solve the above problems, the present invention provides a bonded structure comprising a piezoelectric layer made of a piezoelectric material, a dielectric layer disposed below the piezoelectric layer, and a support substrate bonded to the piezoelectric layer with the dielectric layer sandwiched therebetween, the dielectric layer including a first silicon oxide layer in contact with the piezoelectric layer and a second silicon oxide layer positioned closer to the support substrate than the first silicon oxide layer, the first silicon oxide layer containing a greater amount of argon than the second silicon oxide layer. In this case, a bonded structure can be provided in which the piezoelectric substrate is less likely to peel off even when the piezoelectric substrate is processed after bonding the support substrate and the piezoelectric substrate together.

[0008] Here, the thickness of the first silicon oxide layer can be 10 nm or more and 1000 nm or less. In this case, peeling of the piezoelectric substrate is further reduced. Furthermore, the arithmetic mean roughness of the main surface of the first silicon oxide layer can be 3 nm or less. In this case, peeling of the piezoelectric substrate is further reduced. Furthermore, the argon content in the first silicon oxide layer can be 0.2 mass % or more and 1.0 mass % or less. In this case, the first silicon oxide layer can be formed by sputtering, and peeling of the piezoelectric substrate is further reduced. Furthermore, the thickness of the second silicon oxide layer can be 1000 nm or more and 20000 nm or less. In this case, peeling of the piezoelectric substrate is further reduced.

[0009] The present invention also provides a device including the above bonded structure, which improves the yield of the device.

[0010] Furthermore, the present invention provides a method for manufacturing a bonded structure, including the steps of forming a first silicon oxide layer on a main surface of a piezoelectric substrate made of a piezoelectric material by sputtering with argon gas, thermally oxidizing a support substrate containing silicon to form a second silicon oxide layer on the main surface of the support substrate, and plasma activating and bonding the first silicon oxide layer and the second silicon oxide layer. In this case, a method for manufacturing a bonded structure can be provided in which the piezoelectric substrate is less likely to peel even when the piezoelectric substrate is processed after bonding the support substrate and the piezoelectric substrate. Here, the method can also include a step of mirror-polishing the main surface of the support substrate before thermally oxidizing the support substrate. In this case, the first silicon oxide layer can be formed more uniformly, and the bonding can be more uniform during subsequent bonding steps.

[0011] According to the present invention, it is possible to provide a bonded structure in which the piezoelectric substrate is less likely to peel off even when the piezoelectric substrate is processed after bonding the support substrate and the piezoelectric substrate, and a method for manufacturing the bonded structure, and it is also possible to provide a device using the bonded structure.

[0012] 1 is a diagram showing a bonded body according to the present embodiment; FIG. 2 is a flowchart illustrating a method for manufacturing a bonded body; (A) to (E) are diagrams illustrating the states of the respective steps shown in FIG. 2; FIG. 3 is an observation image of peeling of an LN substrate in level 1; FIG. 4 is an observation image of the state of an LN substrate in level 3; FIG. 5 is an observation image of peeling of an LN substrate in level 6; FIG. 6 is a diagram illustrating a sputtering apparatus used when forming a silicon oxide film on an LN substrate by sputtering; FIG. 7 is an observation image comparing the states before and after heating for levels 3 (Ar flow rate 1.3), 4 (Ar flow rate 1.35), and 6 (Ar flow rate 0.85); and FIG. 8 is a plot of the relationship between the Ar content and the change in the number of defects.

[0013] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0014] 1 is a diagram showing a bonded body 1 according to the present embodiment. The bonded body 1 shown in the figure has a structure in which a piezoelectric layer 11a, a dielectric layer 12, and a support substrate 13 are stacked in this order from the top in the figure.

[0015] The piezoelectric layer 11a is a layer made of a piezoelectric material. The piezoelectric material is selected depending on the application of the bonded body 1. For example, the piezoelectric material is LiNbO ３ (LN) and LiTaO ３ (LT), but is not limited to this, and silicon (Si), gallium arsenide (GaAs), silicon carbide (SiC), gallium nitride (GaN), zinc oxide (ZnO), solid solution ceramics (PZT), etc. may be appropriately selected.

[0016] The dielectric layer 12 is a layer disposed under the piezoelectric layer 11a. In this embodiment, the dielectric layer 12 is made of SiO ２ That is, the dielectric layer 12 is mainly composed of SiO ２ Film and SiO ２ It can also be said to be a layer.

[0017] The dielectric layer 12 is a first silicon oxide (SiO ２ ) layer 12a, and a second silicon oxide (SiO ２ ) layer 12b. The argon content of the first silicon oxide layer 12a is greater than the argon content of the second silicon oxide layer 12b. The argon content of the first silicon oxide layer 12a is preferably 0.2 mass% or more and 1.0 mass% or less. If the argon content is 0.2 mass% or less, it becomes difficult to form the first silicon oxide layer 12a by sputtering. If the argon content exceeds 1.0 mass%, the bonding strength between the piezoelectric layer 11a and the first silicon oxide layer 12a becomes insufficient, resulting in peeling of the piezoelectric layer 11a. The argon content of the second silicon oxide layer 12b is almost zero, below the detection limit.

[0018] The thickness of the first silicon oxide layer 12a is preferably 10 nm to 1000 nm. If the thickness of the first silicon oxide layer 12a is less than 10 nm or more than 1000 nm, the bonding strength between the piezoelectric layer 11a and the first silicon oxide layer 12a is likely to be insufficient, and as a result, peeling of the piezoelectric layer 11a is likely to occur.

[0019] The thickness of the second silicon oxide layer 12b is preferably 1000 nm or more and 20000 nm or less. If the thickness of the second silicon oxide layer 12b is less than 1000 nm or more than 20000 nm, the bonding strength between the piezoelectric layer 11a and the first silicon oxide layer 12a is likely to be insufficient, and as a result, peeling of the piezoelectric layer 11a is likely to occur.

[0020] The support substrate 13 serves as a support for the entire bonded structure 1. The support substrate 13 is bonded to the piezoelectric layer 11a with the dielectric layer 12 sandwiched therebetween. As will be described in detail later, the bonded structure 1 is manufactured by forming a first silicon oxide layer 12a on the piezoelectric layer 11a, forming a second silicon oxide layer 12b on the support substrate 13, and then bonding the first silicon oxide layer 12a and the second silicon oxide layer 12b together. Therefore, the first silicon oxide layer 12a formed on the piezoelectric layer 11a and the second silicon oxide layer 12b formed on the support substrate 13 are bonded to form the dielectric layer 12, and thus the piezoelectric layer 11a and the support substrate 13 are bonded via the dielectric layer 12. Any appropriate substrate may be used as the support substrate 13. The support substrate 13 may be composed of a single crystal or a polycrystalline material. It may also be composed of a metal.

[0021] The material constituting the support substrate 13 is preferably selected from the group consisting of silicon, sialon, sapphire, cordierite, mullite, glass, quartz, crystal, alumina, SUS, iron-nickel alloy (42 alloy), and brass. The thickness of the support substrate 13 is, for example, 0.2 to 1 mm, but any other appropriate thickness can be adopted.

[0022] The silicon may be single crystal silicon, polycrystalline silicon, or high-resistivity silicon, and the support substrate 13 may be SOI (Silicon on Insulator).

[0023] Typically, the sialon is a ceramic obtained by sintering a mixture of silicon nitride and alumina, and for example, Si ６－ｗ Al ｗ Oｗ N ８－ｗ Specifically, sialon has a composition in which alumina is mixed in silicon nitride, and w in the formula indicates the mixing ratio of alumina. w is preferably 0.5 or more and 4.0 or less.

[0024] Typically, the sapphire is Al ２ O ３ The alumina is a single crystal having a composition of Al ２ O ３ The alumina is preferably a translucent alumina.

[0025] Typically, the cordierite is 2MgO.2Al ２ O ３ 5SiO ２ The mullite is a ceramic having a composition of 3Al ２ O ３ 2SiO ２ ~2Al ２ O ３ SiO ２ It is a ceramic having a composition in the range of

[0026] <Device> The structure of the bonded body 1 shown in the figure can be used as the structure of various devices, such as high-frequency devices, power semiconductors, semiconductor lasers, surface acoustic wave (SAW) filters, thin-film piezoelectric MEMS (Micro Electro Mechanical Systems), etc.

[0027] <Description of Manufacturing Method of Bonded Body 1> Next, a manufacturing method of the bonded body 1 will be described. FIG. 2 is a flowchart illustrating the manufacturing method of the bonded body 1. Also, FIGS. 3A to 3E are diagrams showing the states corresponding to the steps shown in FIG. 2. First, a piezoelectric material substrate 11 made of a piezoelectric material is prepared, and a first silicon oxide layer 12a is formed on a main surface of the piezoelectric material substrate 11 (step 101). In this embodiment, sputtering is performed in this step using argon gas. As a result, the first silicon oxide layer 12a is formed on one main surface of the piezoelectric material substrate 11. Specifically, the first silicon oxide layer 12a is formed by reactive sputtering using a reactive sputtering device. That is, the piezoelectric material substrate 11 is placed in the reactive sputtering device. Furthermore, a target made of silicon (Si) is placed in the reactive sputtering device. Furthermore, argon (Ar) gas and oxygen (O ２ Then, silicon constituting the target is sputtered by a sputtering power supply to form a silicon film on the piezoelectric material substrate 11, which is then oxidized by oxygen radicals generated by the oxygen gas to form silicon oxide (SiO ２ As a result, a silicon (SiO ２ ) as a main component, the first silicon oxide layer 12a can be formed.

[0028] Next, a support substrate 13 containing silicon is prepared, and a second silicon oxide layer 12b is formed on the main surface of the support substrate 13 (step 102). In this embodiment, the support substrate is thermally oxidized in this step. As a result, the second silicon oxide layer 12b is formed on the entire surface, including one main surface and the other main surface, of the support substrate 13. Specifically, the second silicon oxide layer 12b is formed by a heat treatment using a heating device such as an oven. That is, the support substrate 13 is placed in the oven. Then, water vapor (H ２ O), or oxygen (O ２ ) gas and heated at a predetermined temperature for a predetermined time, silicon oxide (SiO ２ ) film can be formed.

[0029] It is preferable to include a step of mirror-polishing the main surface of the support substrate 13 before step 102. Mirror-polishing flattens the main surface of the support substrate 13 on which the first silicon oxide layer 12a is to be formed. This allows the first silicon oxide layer 12a to be formed more uniformly, and also allows the two substrates to be bonded more uniformly in a subsequent step.

[0030] Steps 101 and 102 can be considered as a dielectric layer formation process (FIG. 3A) in which a first silicon oxide layer 12a and a second silicon oxide layer 12b are formed on the main surfaces of the piezoelectric material substrate 11 and the support substrate 13. The order of steps 101 and 102 may be reversed. The first silicon oxide layer 12a and the second silicon oxide layer 12b may also be polished and flattened. This improves the bonding strength when they are bonded in a later step.

[0031] Next, the first silicon oxide layer 12a and the second silicon oxide layer 12b are activated by plasma (step 103: activation step) (FIG. 3B). ２ Plasma can be used, and as a result, as shown in FIG. ２ is activated, and a hydroxyl group (OH group) is generated as a hydrophilic functional group. Therefore, this process can also be regarded as a hydrophilization process in which the surfaces of the first silicon oxide layer 12 a and the second silicon oxide layer 12 b are made hydrophilic by plasma.

[0032] Furthermore, the surfaces of the first silicon oxide layer 12a and the second silicon oxide layer 12b after the activation step are bonded together (step 104: bonding step) (FIG. 3(D)). The bonding is performed, for example, by bringing the surfaces of the first silicon oxide layer 12a and the second silicon oxide layer 12b into contact with each other and pressing them together with a predetermined pressure. As a result, the piezoelectric material substrate 11 and the support substrate 13 are bonded together via the first silicon oxide layer 12a and the second silicon oxide layer 12b.

[0033] The bonded piezoelectric material substrate 11 and support substrate 13 are then heated (step 105: heating step) (FIG. 3(E)). Heating is performed, for example, by placing the bonded piezoelectric material substrate 11 and support substrate 13 in a heating device such as an oven at a predetermined temperature and time. The hydroxyl groups generated on the surfaces of the first silicon oxide layer 12a and the second silicon oxide layer 12b are covalently bonded by the heating. The first silicon oxide layer 12a and the second silicon oxide layer 12b are then integrated to form the dielectric layer 12. As a result, the piezoelectric material substrate 11 and support substrate 13 are firmly bonded via the dielectric layer 12. At this time, the following reaction occurs: [Si-OH] + [OH + Si] → [Si-O-Si] + H ２ The reaction of O occurs. The heating step can also be regarded as a step of annealing the bonded piezoelectric material substrate 11 and support substrate 13 (annealing step).

[0034] Next, the heated piezoelectric material substrate 11 is ground (step 106: grinding step). In this embodiment, the piezoelectric material substrate 11 is ground to make it thinner, thereby forming the piezoelectric layer 11a shown in FIG. 1. The support substrate 13 may also be ground at the same time, or the edges of the piezoelectric material substrate 11 and the support substrate 13 may be ground. The bonded body 1 can be manufactured by the above steps.

[0035] A silicon substrate was prepared as the support substrate 13, and both the front and back surfaces were polished to a mirror finish. Then, a silicon oxide film (SiO ２ ) was formed by thermal oxidation. The thickness of the silicon oxide film was 1000 nm. Next, a lithium niobate (LN) substrate was prepared as the piezoelectric material substrate 11, and a silicon oxide film was formed on the LN substrate as the first silicon oxide layer 12a. The silicon oxide film on the LN substrate was formed by sputtering, and the thickness of the silicon oxide film was varied under the conditions shown in Table 1. That is, the thickness was varied in seven ways (levels 1 to 7): 0 nm, 5 nm, 10 nm, 15 nm, 20 nm, 1000 nm, and 1500 nm.

[0036] The silicon substrate and the LN substrate were then plasma activated and bonded to form a wafer. The bonded wafer was then heated in an inert oven at 100°C for 10 hours in a non-oxidizing atmosphere, and the surface of the LN substrate was then polished with a #1000 grinding stone.

[0037] Table 1 shows the results of the evaluation of whether or not peeling occurred on the surface of the LN substrate after polishing. When the silicon oxide film thickness was 0 nm (i.e., no silicon oxide film was formed on the LN substrate) (Level 1), peeling of the LN substrate was observed after polishing. In this case, peeling is thought to occur due to insufficient bonding strength between the LN substrate and the silicon oxide film on the support substrate 13 side. An observation image of the peeling of the LN substrate in this case is shown in Figure 4. As shown in Figure 4, significant peeling can be seen. On the other hand, it was found that the LN substrate can be processed without peeling if the silicon oxide film on the LN substrate side is 10 nm or thicker. As an example of this case, Figure 5 shows an observation image of the state of an LN substrate with a silicon oxide layer thickness of 10 nm (Level 3). As shown in Figure 5, it can be seen that no peeling occurred. Furthermore, when the silicon oxide film thickness was 1000 nm, slight, but very small, peeling was observed after polishing. This is thought to be due to the increased arithmetic mean roughness (Ra) of the thicker film. Figure 6 shows an image of the peeling of the LN substrate at this time (Level 6). As shown in Figure 6, small peeling can be seen around the periphery of the LN substrate. However, this level of peeling does not pose a problem for subsequent use as a wafer and is within the acceptable range. Furthermore, when the silicon oxide film thickness was 1500 nm, unacceptable peeling was observed after polishing. These results suggest that to enhance the bonding strength between the LN substrate and the silicon oxide film formed on the LN substrate, it is desirable to form a silicon oxide film with a thickness of 10 nm to 1000 nm on the LN substrate. Furthermore, from the perspective of arithmetic mean roughness (Ra), Table 1 indicates that the arithmetic mean roughness (Ra) of the silicon oxide film is desirably 3 nm or less.

[0038]

[0039] Next, in order to further improve the bonding strength, sputtering conditions were optimized and an accelerated test was also performed to evaluate the bonding strength. Figure 7 is a diagram showing a sputtering apparatus 20 used when forming a silicon oxide film on an LN substrate by sputtering. The illustrated sputtering apparatus 20 uses silicon (Si) as a target 21 and performs reactive sputtering on an LN substrate 22. A sputtering power supply 23 is connected to the target 21 and the LN substrate 22, and a voltage is applied between them. The sputtering apparatus 20 contains argon (Ar) gas, which is an inert gas, and oxygen (O ２ ) gas is introduced to perform reactive sputtering. That is, the argon gas is discharged to become positive ions, which collide with the target 21, which is the cathode. This causes the silicon constituting the target 21 to be ejected and adhere to the LN substrate 22. Also, the oxygen gas is discharged to become oxygen radicals, which undergo an oxidation reaction with the silicon adhered to the LN substrate 22, forming silicon oxide (SiO ２ ) As a result, a silicon oxide film containing silicon oxide as a main component is formed on the surface of the LN substrate 22.

[0040] The parameters of the sputtering device 20 are the flow rate of argon gas (Ar flow rate), the flow rate of oxygen gas (O ２ Examples of the parameters include the flow rate of the Ar gas and the discharge output of the target 21. In this embodiment, the Ar flow rate was varied while the other conditions were kept constant, and a silicon oxide film of 10 nm was formed on the LN substrate 22. As shown in Table 2, the Ar flow rate was varied in seven ways (levels 1 to 7), with standard condition being 1. On the other hand, thermal oxidation was used for the silicon substrate as in the previous example, and a silicon oxide film of 1000 nm was formed under the same film formation conditions.

[0041]

[0042] Thereafter, the silicon oxide film surfaces on both the silicon substrate and the LN substrate 22 were activated in the same manner, bonded, and heated. The surface of the LN substrate 22 was then polished until the film thickness of the LN substrate 22 was 1000 nm. At this point, no peeling of the LN substrate 22 was observed as before. Next, the bonded wafer was heated in an oven at 500°C for 10 hours. The surface of the LN substrate 22 was visually observed before and after heating using an optical appearance inspection device, and the amount of defects on the surface, i.e., the extent of LN peeling, was evaluated. Defects of 10 μm or larger in size were counted.

[0043] Table 3 shows the change in the number of defects before and after heating. It was found that the number of defects increased when the Ar flow rate exceeded 1.3. In this case, it is considered that the greater the number of defects, the more insufficient the bonding strength between the LN substrate and the silicon oxide film.

[0044]

[0045] 8 shows images comparing the results before and after heating for levels 3 (Ar flow rate 1.3), 4 (Ar flow rate 1.35), and 6 (Ar flow rate 0.85). It is clear from these images that the number of defects increases when the Ar flow rate is high.

[0046] Next, the Ar content in the silicon oxide films of levels 1 to 7 was analyzed using Rutherford Backscattering Spectrometry (RBS). The results are shown in Table 3. Figure 9 plots the relationship between Ar content and the change in the number of defects. This shows that an increase in the number of defects (more than 100) can be suppressed by keeping the Ar content below 1% by mass. Level 7 showed a low number of defects, but the Ar flow rate was kept to a minimum, resulting in unstable plasma during sputtering. Therefore, the Ar content of 0.2% by mass shown in this level represents the minimum Ar content in the silicon oxide film that can be formed by sputtering. For reference, the Ar content in the silicon oxide film on the silicon substrate side formed by thermal oxidation was also analyzed using RBS, but the amount was below the detection limit. Argon in the silicon oxide film formed by sputtering can be generated as outgassing during heating. It is believed that a silicon oxide film containing a large amount of argon generates argon gas as an outgas when heated, which is the starting point for peeling off the LN substrate 22. From the above, it can be seen that in order to further strengthen the bonding strength between the LN substrate 22 and the silicon oxide film formed on the LN substrate 22, it is desirable that the Ar content in the silicon oxide film be 0.2 mass % or more and 1.0 mass % or less.

[0047] Next, the thickness of the silicon oxide film on the silicon substrate side formed by thermal oxidation was varied among five levels (Levels 1 to 5): 1000 nm, 10,000 nm, 15,000 nm, 20,000 nm, and 25,000 nm, and the degree of LN peeling progression was evaluated. The film formation conditions for the silicon oxide film on the LN substrate 22 were Level 1 in Table 3, and the film thickness was uniform at 10 nm. Next, the bonded wafers were heated in an oven at 500°C for 10 hours in the same manner as described above. The degree of LN peeling progression was then evaluated before and after heating using an optical visual inspection device.

[0048] The evaluation results are shown in Table 4. It was found that the number of defects in the silicon oxide film on the silicon substrate side tended to increase slightly when the film thickness exceeded 20,000 nm. Table 4 also shows the arithmetic mean roughness (Ra) of the silicon oxide film surface on the silicon substrate side. The arithmetic mean roughness (Ra) tends to increase as the silicon oxide film thickness increases, and this is thought to have influenced the degree of progression of LN peeling. Polishing the surface of the silicon oxide film could be considered to reduce the arithmetic mean roughness (Ra), but in this case, the silicon oxide film may absorb moisture during the polishing process, raising concerns about outgassing during heating as mentioned above. Therefore, for bonding without polishing, it is preferable to set the thickness to about 20,000 nm.

[0049]

[0050] Although the present embodiment has been described above, the technical scope of the present invention is not limited to the scope of the above embodiment. It is clear from the claims that various modifications and improvements to the above embodiment are also included in the technical scope of the present invention.

[0051] REFERENCE SIGNS LIST 1... Bonded body, 11... Piezoelectric material substrate, 11a... Piezoelectric layer, 12... Dielectric layer, 12a... First silicon oxide layer, 12b... Second silicon oxide layer, 13... Support substrate, 20... Sputtering apparatus, 21... Target, 22... LN substrate

Claims

1. A bonded body comprising: a piezoelectric layer made of a piezoelectric material; a dielectric layer disposed under the piezoelectric layer; and a support substrate bonded to and sandwiching the dielectric layer between the piezoelectric layer and the dielectric layer, wherein the dielectric layer includes a first silicon oxide layer in contact with the piezoelectric layer and a second silicon oxide layer located closer to the support substrate than the first silicon oxide layer, and the argon content of the first silicon oxide layer is greater than the argon content of the second silicon oxide layer.

2. The bonded body according to claim 1, wherein the thickness of the first silicon oxide layer is 10 nm or more and 1000 nm or less.

3. The bonded body according to claim 1, wherein the arithmetic mean roughness of the main surface of said first silicon oxide layer is 3 nm or less.

4. The bonded body according to claim 1, wherein the argon content in the first silicon oxide layer is 0.2% by mass or more and 1.0% by mass or less.

5. The bonded body according to claim 1, wherein the thickness of the second silicon oxide layer is not less than 1,000 nm and not more than 20,000 nm.

6. A device comprising a joint according to any one of claims 1 to 5.

7. A method for manufacturing a bonded body, comprising: forming a first silicon oxide layer on a main surface of a piezoelectric substrate made of a piezoelectric material by sputtering with the introduction of argon gas; forming a second silicon oxide layer on a main surface of a support substrate containing silicon by thermally oxidizing the support substrate; and plasma activating and bonding the first silicon oxide layer and the second silicon oxide layer.

8. The method for producing a bonded body according to claim 7, further comprising the step of mirror-polishing a main surface of said support substrate before thermally oxidizing said support substrate.