Method for manufacturing composite substrate

Abstract

The method for manufacturing a composite substrate includes: forming an intermediate layer on a support substrate; respectively irradiating FAB on the surface of the piezoelectric material substrate and the surface of the intermediate layer formed on the support substrate; the surface of the piezoelectric material substrate is further irradiated with FAB, and a sputtering film containing the material of the piezoelectric material substrate is formed on the surface of the middle layer; a bonding step for bonding the piezoelectric material substrate and the intermediate layer on which the sputtering film is formed to obtain a bonded body having the waveguide substrate; and irradiating the joined body with laser light along the surface direction of the composite substrate, and forming the composite substrate using the joined body irradiated with the laser light.

Description

Technical Field

[0001] This invention relates to a method for manufacturing a composite substrate. Background Technology

[0002] Previously, composite substrates were known to be formed by bonding a piezoelectric substrate made of materials such as LN (LiNbO3: lithium niobate) or LT (LiTaO3: lithium tantalate) with a support substrate made of materials such as Si, and were used in surface wave devices. One known method for fabricating such composite substrates involves activating each bonding surface of the piezoelectric substrate and the support substrate by irradiating them with FAB (Fast Atom Beam), and then directly bonding these bonding surfaces together. However, this method suffers from the following problem: the bonding strength between the substrates is low, and they may peel off during post-bonding processing.

[0003] Therefore, as a technology to solve the above-mentioned problem, the technology of Patent Document 1 is known. Patent Document 1 describes a method in which a silicon oxide (SiO2) film is formed on a support substrate as an intermediate layer, and a bonding layer made of a material such as silicon nitride (Si3N4) is further formed on the film, and the piezoelectric substrate and the bonding layer are directly bonded together. This method improves the bonding strength between the piezoelectric substrate and the support substrate and prevents peeling after bonding.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2017 / 163722 Summary of the Invention

[0007] In the composite substrate with the structure of Patent Document 1, a bonding layer made of Si3N4 is provided. However, when using piezoelectric material substrates such as LN (LiNbO3) or LT (LiTaO3) as functional layers, from the viewpoint of encapsulating energy (light, or elastic waves, etc.), there is a requirement for a composite substrate without a bonding layer.

[0008] To obtain a composite substrate without a bonding layer, even when bonding the piezoelectric substrate and the support substrate with a silicon oxide intermediate layer is performed during the composite substrate manufacturing process, sufficient bonding strength cannot be achieved, necessitating improvement. The same applies when the piezoelectric substrate and the support substrate are directly bonded. Therefore, there is a problem regarding the bonding strength between the intermediate layer or support substrate disposed on the support substrate and the piezoelectric material substrate made of LiNbO3 or LiTaO3.

[0009] The present invention was made in view of the above circumstances, and its main objective is to realize a method for manufacturing a composite substrate that improves the bonding strength between an intermediate layer disposed on a support substrate or a support substrate and a piezoelectric material substrate and has good light propagation characteristics.

[0010] The first aspect of the present invention relates to a method for manufacturing a composite substrate comprising the following steps: forming an intermediate layer comprising at least one of SiO2, MgF2, and CaF2 on a support substrate; irradiating the surface of a piezoelectric material substrate formed by using LiNbO3 or LiTaO3 as a material and the surface of the intermediate layer formed on the support substrate with a high-speed atomic beam; further irradiating the surface of the piezoelectric material substrate with the high-speed atomic beam to form a sputtered film comprising the material of the piezoelectric material substrate on the surface of the intermediate layer; bonding the piezoelectric material substrate and the intermediate layer on which the sputtered film is formed to obtain a bond; irradiating the bond along the surface direction of the composite substrate with a laser; and forming the composite substrate using the bond irradiated with the laser.

[0011] The second aspect of the present invention relates to a method for manufacturing a composite substrate, comprising the following steps: irradiating the surface of a piezoelectric material substrate formed by using LiNbO3 or LiTaO3 as a material and the surface of a support substrate containing SiO2, MgF2 or CaF2 with a high-speed atomic beam; further irradiating the surface of the piezoelectric material substrate with the high-speed atomic beam to form a sputtered film made of the material of the piezoelectric material substrate on the surface of the support substrate; bonding the piezoelectric material substrate and the support substrate on which the sputtered film is formed to obtain a bond; irradiating the bond along the surface direction of the composite substrate with a laser; and forming the composite substrate using the bond irradiated with the laser.

[0012] Invention Effects

[0013] According to the present invention, a method for manufacturing a composite substrate that improves the bonding strength between an intermediate layer disposed on a support substrate or a support substrate and a piezoelectric material substrate and has good light propagation characteristics can be realized. Attached Figure Description

[0014] Figure 1 This is a diagram showing the general structure of the composite substrate according to the first embodiment of the present invention.

[0015] Figure 2 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the first embodiment of the present invention.

[0016] Figure 3 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the first embodiment of the present invention.

[0017] Figure 4 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the first embodiment of the present invention.

[0018] Figure 5 This is a diagram showing the general structure of the composite substrate according to the second embodiment of the present invention.

[0019] Figure 6 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the second embodiment of the present invention.

[0020] Figure 7 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the second embodiment of the present invention.

[0021] Figure 8 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the second embodiment of the present invention.

[0022] Figure 9 This is a diagram illustrating the performance evaluation system for composite substrates. Detailed Implementation

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings; however, the present invention is not limited to these embodiments. Furthermore, the accompanying drawings make the description clearer, and therefore, the width, thickness, shape, etc., of each part are sometimes schematically shown compared to the embodiments; however, this is merely an example and does not limit the interpretation of the present invention.

[0024] (First Implementation)

[0025] Figure 1 This is a diagram showing a schematic structure of the composite substrate according to the first embodiment of the present invention. The composite substrate 100 in this embodiment is used, for example, as an optical element constituting an optical waveguide, and has a structure in which a piezoelectric material substrate is bonded to a support substrate 30 via an intermediate layer 20. Figure 1 (a) is a schematic cross-sectional view of the composite substrate 100. Figure 1 (b) is a schematic plan view of the composite substrate 100.

[0026] Figure 1 The x, y, z coordinate axes given in the figure correspond to the crystal axis of the waveguide substrate 10.

[0027] In the first embodiment, the piezoelectric material substrate is a waveguide substrate 10 including an optical waveguide. Its surface is shaped into a straight line of a predetermined width using dry etching, cutting, laser processing, or the like, thereby forming grooves 60 that extend linearly along the crystal axis x-direction of the waveguide substrate 10. These grooves 60 are provided at two points on the surface of the waveguide substrate 10 at a certain interval. Thus, a ridge 50 with a trapezoidal cross-section is formed in the portion sandwiched between a pair of parallel grooves 60. This ridge 50 is utilized as an optical waveguide.

[0028] It should be noted that the waveguide substrate 10 is made of piezoelectric materials such as LiNbO3 (lithium niobate) or LiTaO3 (lithium tantalate). Hereinafter, LiNbO3 and LiTaO3 are sometimes referred to as "LN" and "LT," respectively. The waveguide substrate 10 includes a bonding interface 40 formed in the bonding process described later.

[0029] An intermediate layer 20 is disposed on the support substrate 30 and positioned between the waveguide substrate 10 and the support substrate 30. For energy sealing purposes, the intermediate layer 20 is made of a low-refractive-index material, preferably a material with a refractive index of 1.8 or less, such as containing at least one of SiO2, MgF2, and CaF2, with SiO2 being the most preferred. It should be noted that if the support substrate 30 is made of SiO2, MgF2, or CaF2, and the refractive index of the support substrate 30 is lower than that of the waveguide substrate 10, the intermediate layer 20 may not be necessary.

[0030] The intermediate layer 20 can be formed using any suitable method. For example, it can be formed using physical evaporation such as sputtering, vacuum evaporation, ion beam assisted evaporation (IAD), chemical evaporation, or atomic layer deposition (ALD). The formation of the intermediate layer 20 can be carried out, for example, at room temperature (25°C) to 300°C.

[0031] The support substrate 30 supports the waveguide substrate 10. Any suitable substrate can be used as the support substrate 30. The support substrate 30 can be made of a single crystal or a polycrystalline material. Alternatively, it can be made of metal. The waveguide substrate 10 and the support substrate 30 are bonded together by an intermediate layer 20.

[0032] The material constituting the support substrate 30 is preferably selected from the group consisting of silicon, silicon aluminum oxynitride ceramic, sapphire, cordierite, andalusite, glass, quartz, crystal, alumina, SUS, iron-nickel alloy (42 alloy), MgF2, CaF2, and brass. The thickness of the support substrate 30 is, for example, 0.3 to 1 mm, but any other suitable thickness may be used.

[0033] The silicon mentioned above can be monocrystalline silicon, polycrystalline silicon, or high-resistivity silicon. Additionally, the support substrate 30 can be SOI (Silicon on Insulator).

[0034] Typically, the aforementioned silicon-aluminum-oxygen-nitrogen ceramics are ceramics obtained by sintering a mixture of silicon nitride and aluminum oxide, for example, having a silicon content of 0.5%. 6-w Al w O w N 8-w The composition is indicated by the formula. Specifically, the silicon-aluminum-oxygen-nitrogen ceramic has a composition in which alumina is mixed in silicon nitride, where w represents the mixing ratio of alumina. w is preferably 0 or more and 4.2 or less, more preferably 0.5 or more and 4.0 or less.

[0035] Typically, the sapphire described above is a single crystal with an Al2O3 composition, and the alumina described above is a polycrystalline material with an Al2O3 composition. The alumina is preferably a transparent alumina.

[0036] Representatively, the cordierite mentioned above is a ceramic having a composition of 2MgO·2Al2O3·5SiO2, and the andalusite mentioned above is a ceramic having a composition in the range of 3Al2O3·2SiO2 to 2Al2O3·SiO2.

[0037] It should be noted that, although not illustrated, the composite substrate 100 may further have any number of layers. The type, function, number, combination, and arrangement of such layers can be appropriately set according to the purpose.

[0038] The composite substrate 100 can be manufactured in any suitable shape. In one embodiment, the composite substrate 100 can be manufactured in the form of a so-called wafer. In addition, the size of the composite substrate 100, for example, the diameter of the wafer (substrate) is 50 mm to 150 mm, can be appropriately set according to the purpose.

[0039] Figure 2 , Figure 3 as well as Figure 4 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the first embodiment of the present invention.

[0040] Figure 2 (a) shows a preparation step in the manufacturing process of the composite substrate 100. In this step, a support substrate 30 is prepared.

[0041] Figure 2 (b) shows the film formation process of the intermediate layer 20 in the manufacturing process of the composite substrate 100. In this process, in Figure 2In the preparation process of (a), an intermediate layer 20 is formed on the surface of the support substrate 30 prepared in the preparation process, for example, by forming an amorphous SiO2 film of a specified thickness.

[0042] Figure 2 (c) shows the activation step in the manufacturing process of the composite substrate 100. In this step, a substrate of a specified thickness, namely the LN substrate 10A, is prepared, for example, by using LN as a material. Figure 2 In the film formation process of (b), the intermediate layer 20 and the LN substrate 10A formed on the surface of the support substrate 30 are activated by irradiating their respective surfaces with a high-speed atomic beam (hereinafter referred to as FAB) using an inactive gas such as Ar for a specified time. The irradiation time of FAB is preferably, for example, about 15 seconds. It should be noted that, as described above, an LT substrate can also be used instead of an LN substrate; however, in the following description, the case including the LT substrate is referred to as "LN substrate 10A".

[0043] Figure 2 (d) shows the sputtering process in the manufacturing process of the composite substrate 100. In this process, in Figure 2 In the activation process (c), the FABs on the intermediate layer 20 and the LN substrate 10A are irradiated respectively. Irradiation of the FABs on the intermediate layer 20 side is stopped, while irradiation of the FABs on the LN substrate 10A side is continued for a predetermined time. The irradiation time of the FABs at this point is... Figure 2 The total irradiation time in the activation process (c) is, for example, about 3 to 10 minutes, preferably 4 to 7 minutes. Thus, the LN constituting the LN substrate 10A is sputtered and attached to the surface of the intermediate layer 20, and a sputtered film 21 made of the same material as the LN substrate 10A is formed on the intermediate layer 20 side.

[0044] Figure 3 (e) shows a bonding process in the manufacturing process of the composite substrate 100. In this process, the bonding process is performed on the composite substrate 100. Figure 2 In the activation process of (c), the LN substrate 10A irradiated with FAB, and Figure 2 In the sputtering process (d), the intermediate layer 20 on which the sputtered film 21 is formed is bonded to form a bond. Thus, the LN substrate 10A and the sputtered film 21 are bonded together and become integrated, with the bonding interface 40 formed inside the LN substrate 10A. At this time, three layers (first layer 11, second layer 12, and third layer 13) are formed near the bonding interface 40 in the LN substrate 10A (see reference). Figure 3 (f) in the first layer 11: does not contain Figure 2In the activation process (c), the second layer 12, which is irradiated with inactive gas atoms such as Ar in the form of FAB, is disposed on the side closer to the intermediate layer 20 than the first layer 11 and contains the aforementioned inactive gas atoms. The third layer 13 is, for example, disposed in contact with the intermediate layer 20 on the side closer to the intermediate layer 20 than the first layer 11 and the second layer 12, and contains either no aforementioned inactive gas atoms or contains them at a lower concentration than the second layer 12. The first layer 11 is composed of a crystal of LN or LT, which is the material of the LN substrate 10A. The third layer 13 is an amorphous film obtained by amorphizing LN or LT. The second layer 12 is also a crystal of LN or LT, like the first layer 11, or an amorphous film obtained by amorphizing LN or LT, like the third layer 13. These layers sometimes contain: Figure 2 In the sputtering process (d), other atomic species, such as Fe atoms, Al atoms, or Cr atoms, are mixed into the second layer 12 or the third layer 13, for example, the fixture or platform portion constituting the LN substrate 10A. Details of these layers are described below. It should be noted that in... Figure 3 After (e) in the middle, with Figure 2 (a) in Figure 2 Compared to (d) in the previous diagram, the positional relationship between the LN substrate 10A, the intermediate layer 20, and the support substrate 30 is shown upside down.

[0045] Figure 3 (f) shows a thin-plate processing step in the manufacturing process of the composite substrate 100. In this step, for... Figure 3 The bonded body after the bonding process shown in (e) is thinned by grinding the LN substrate 10A to a specified thickness. For example, grinding, CMP (Chemical Mechanical Polishing), or surface planarization using a gas cluster ion beam can be used to achieve thinning of the LN substrate 10A.

[0046] Figure 3 (g) shows the ridge processing step in the manufacturing process of the composite substrate 100. In this step, in Figure 3 In the thin-plate processing step (f), straight grooves 60 are provided at two locations on the surface of the thinned LN substrate 10A at certain intervals, thereby forming ridges 50 that function as optical waveguides. For example, the grooves 60 can be formed by dry etching such as laser processing or RIE (Reactive Ion Etching) on ​​the surface of the LN substrate 10A.

[0047] Figure 4 (h) shows the thermal annealing process in the manufacturing process of the composite substrate 100. In this process, the thermal annealing process is utilized. Figure 3 In step (g), the ridge processing step forms a bonding body with a groove 60 on the surface of the LN substrate 10A, which is then heated to a predetermined temperature. The heating temperature is preferably, for example, around 300 to 450°C, and more preferably 400 to 450°C. As a result, in the composite substrate 100 manufactured from this bonding body, the light propagation characteristics of the waveguide substrate 10, including the ridge 50, can be improved, and light loss when the ridge 50 is used as a waveguide can be reduced.

[0048] The inventors of this invention have confirmed through experiments that the light propagation characteristics are improved by utilizing the aforementioned thermal annealing process. The reason for improving the light propagation characteristics of the waveguide substrate 10 through the thermal annealing process can be attributed, for example, to: Figure 2 The activation process in (c) or Figure 2 In the sputtering process of (d), a portion of the LN or LT in the waveguide substrate 10 that has been irradiated by FAB and is amorphized is heated to recrystallize.

[0049] It should be noted that inactive gas atoms, and other atomic species mixed into the second layer 12 or the third layer 13 during the aforementioned sputtering process, may sometimes be due to... Figure 4 In the heat annealing process (h), the LN substrate 10A is heated to diffuse into other layers, and the degree of diffusion varies depending on the heating temperature or heating time. That is, the content of Fe atoms, Al atoms, or Cr atoms in the first layer 11, the second layer 12, and the third layer 13 varies depending on the heating temperature or heating time in the heat annealing process. It should be noted that in the second and third layers, the content of Fe atoms is preferably 0.5 to 20 atomic%, the content of Al atoms is preferably 0.5 to 8.5 atomic%, and the content of Cr atoms is preferably 0.5 to 4.5 atomic%. In addition, the content of inactive gas atoms in the second layer is preferably 2.5 to 3.5 atomic%, and the content of inactive gas atoms in the third layer is preferably 0 to 1.1 atomic%.

[0050] It should be noted that as long as the above-described heat annealing process is implemented... Figure 3 The joining process in (e) can be performed at any time afterward. For example, it can be performed for applications involving... Figure 3 The bond between the LN substrate 10A and the intermediate layer 20 obtained by the bonding process in (e) is subjected to a heat annealing process, and then the bonding process is carried out. Figure 3 The thin plate processing procedure in (f) of the text, or Figure 3 The ridge processing step (g) in the middle. In addition, even if the thermal annealing process is not performed, the optical propagation characteristics of the waveguide substrate 10 can be improved by performing the optical annealing process described later. Therefore, the thermal annealing process can be performed as needed or it can be omitted.

[0051] Figure 4Image (i) shows the photo-annealing process in the manufacturing process of the composite substrate 100. In this process, for the use of… Figure 3 In step (g), the ridge processing step forms a groove 60 on the surface of the LN substrate 10A and further performs the required steps. Figure 4 In the heat annealing process (h) of the bonding body, an irradiation range 51 is set corresponding to the ridge 50 sandwiched by the groove 60. Laser is irradiated along the surface direction (x direction) of the composite substrate 100 formed using the bonding body, with respect to this irradiation range 51. The laser output power and irradiation time are preferably 100mW or more and 4 minutes or more, respectively. Thus, the laser passes through using the ridge 50 as an optical waveguide. It should be noted that it is not necessary for the entire irradiation range 51 to fall within the ridge 50; a portion of the irradiation range 51 may be offset from the ridge 50.

[0052] In this embodiment, by performing the above-described optical annealing process, the light propagation characteristics of the waveguide substrate 10 in the ridge 50 can be improved in the composite substrate 100 manufactured from the bonding body, thereby reducing light loss. It should be noted that the reasons for improving the light propagation characteristics of the waveguide substrate 10 through the optical annealing process will be explained below.

[0053] Through the above processes, Figure 1 The structure shown produces a composite substrate 100 with good light propagation characteristics.

[0054] (Second Implementation)

[0055] Figure 5 This is a diagram illustrating the general structure of the composite substrate according to the second embodiment of the present invention. The composite substrate 110 in this embodiment is different from that described in the first embodiment. Figure 1 The composite substrate 100 has a structure in which the waveguide substrate 10 is bonded to the support substrate 30 without the aid of the intermediate layer 20. Figure 5 (a) is a schematic cross-sectional view of the composite substrate 110. Figure 5 (b) is a schematic plan view of the composite substrate 110.

[0056] Figure 5 The x, y, z coordinate axes shown correspond to the crystal axis of the waveguide substrate 10.

[0057] As described above, by using a substrate made of SiO2, MgF2, or CaF2 as the support substrate 30, even when the refractive index of the support substrate 30 is lower than that of the waveguide substrate 10, such as... Figure 5 The structure shown can be used to form a composite substrate 110 that can be used as an optical element constituting an optical waveguide, even without the intermediate layer 20.

[0058] It should be noted that, similar to the first embodiment described above, the composite substrate 110 may further have any layers. The type, function, number, combination, and arrangement of such layers can be appropriately set according to the purpose. In addition, the composite substrate 110 can be manufactured in any suitable shape according to the purpose.

[0059] Figure 6 , Figure 7 as well as Figure 8 This is a diagram illustrating an example of the manufacturing process of the composite substrate according to the second embodiment of the present invention.

[0060] Figure 6 Image (a) shows a preparation step in the manufacturing process of the composite substrate 110. This step is similar to that described in the first embodiment. Figure 2 The support substrate 30 is prepared in the same manner as in step (a) of the first embodiment. It should be noted that, in this embodiment, unlike the first embodiment, the step of forming the intermediate layer 20 on the support substrate 30 is omitted.

[0061] Figure 6 (b) shows the activation process in the manufacturing process of the composite substrate 110. In this process, for example, an LN substrate 10A of a specified thickness is prepared, targeting... Figure 6 The surface of the support substrate 30 and the LN substrate 10A prepared in the preparation step (a) are the same as those described in the first embodiment. Figure 2 Similarly, in step (c), the respective surfaces are irradiated with an inactive gas such as Ar for a specified time using FAB to activate the atomic species, thereby performing an activation treatment.

[0062] Figure 6 (c) shows the sputtering process in the manufacturing process of the composite substrate 110. In this process, the sputtering process is similar to that described in the first embodiment. Figure 2 Similarly, in process (d) of the above, Figure 6 In the activation process (b), the FABs on the support substrate 30 and the LN substrate 10A are irradiated respectively. Irradiation of the FABs on the support substrate 30 side is stopped, while irradiation of the FABs on the LN substrate 10A side is continued for a predetermined time. The irradiation time of the FABs at this time is... Figure 6 The total irradiation time in the activation process (b) is, for example, about 3 to 10 minutes, preferably 4 to 7 minutes. Thus, the LN constituting the LN substrate 10A is sputtered and attached to the surface of the support substrate 30, and a sputtered film 21 made of the same material as the LN substrate 10A is formed on the support substrate 30 side.

[0063] Figure 7 (d) shows a bonding process in the manufacturing process of the composite substrate 110. In this process, the bonding process described in the first embodiment... Figure 3 Similarly, in step (e), Figure 6 In the activation process of (b) in the middle, the LN substrate 10A irradiated with FAB and Figure 6 In the sputtering process (c), the support substrate 30 on which the sputtered film 21 is formed is bonded to form a bond. Thus, the LN substrate 10A and the sputtered film 21 are bonded together as an integral unit, and the bonding interface 40 between them is formed inside the LN substrate 10A. It should be noted that in Figure 7 After (d) in the middle, with Figure 6 (a) in Figure 6 Compared to (c) in the previous diagram, the positional relationship between the LN substrate 10A and the support substrate 30 is shown upside down.

[0064] Figure 7 (e) shows a thin-plate processing step in the manufacturing process of the composite substrate 110. In this step, the process described in the first embodiment... Figure 3 Similarly, for process (f) in the middle, Figure 7 The bonded body after the bonding process shown in (d) is thinned by grinding the LN substrate 10A to a specified thickness.

[0065] Figure 7 (f) shows the ridge processing step in the manufacturing process of the composite substrate 110. In this step, the process described in the first embodiment... Figure 3 Similarly, in process (g) of the middle, Figure 7 In the thin-plate processing step (e), straight grooves 60 are provided at two locations on the surface of the thinned LN substrate 10A, thereby forming ridges 50 that function as optical waveguides.

[0066] Figure 8 (g) shows the thermal annealing process in the manufacturing process of the composite substrate 110. In this process, the process described in the first embodiment... Figure 4 Similarly, the (h) process will utilize... Figure 7 In step (f), the ridge processing step involves heating the bonding body, on the surface of the LN substrate 10A, where the groove 60 is formed, to a predetermined temperature. The preferred heating temperature is, for example, around 300–450°C, and more preferably 400–450°C. It should be noted that, similar to the first embodiment, this process is repeated only when implementing… Figure 7 Following the joining process in (d), a heat annealing process can be performed at any time. For example, it can be performed on [a specific type of material]. Figure 7 The bond between the LN substrate 10A and the support substrate 30 obtained by the bonding process in step (d) is subjected to a heat annealing process, and then subjected to... Figure 7 The thin plate processing procedure in (e) of the text, or Figure 7The ridge processing step (f) in the diagram. Additionally, the hot annealing step can be performed as needed, or it can be omitted.

[0067] Figure 8 (h) shows the photo-annealing process in the manufacturing process of the composite substrate 110. In this process, the photo-annealing process is similar to that described in the first embodiment. Figure 4 Similarly, for process (i) in the middle, the use of Figure 7 In step (f), the ridge processing step forms a groove 60 on the surface of the LN substrate 10A and further performs the following steps as needed: Figure 8 In the heat annealing process (g) of this assembly, an irradiation range 51 is set corresponding to the ridge 50 sandwiched by the groove 60. Laser light is irradiated along the surface direction (x-direction) of the composite substrate 110 formed using this assembly, with respect to the irradiation range 51. The laser output power and irradiation time are preferably 100mW or more and 4 minutes or more, respectively. Thus, by using the ridge 50 as an optical waveguide to allow laser light to pass through, the light propagation characteristics of the waveguide substrate 10 in the ridge 50 are improved in the composite substrate 110 manufactured by this assembly, thereby reducing light loss.

[0068] Through the above processes, Figure 5 The structure shown is used to manufacture a composite substrate 110 with good light propagation characteristics.

[0069] (Light annealing process)

[0070] Here, through Figure 4 (i) Figure 8 The rationale for improving the light propagation characteristics of the waveguide substrate 10 using the optical annealing process described in section (h) is as follows: When laser light is irradiated onto the irradiation range 51 corresponding to the ridge 50 during the optical annealing process, the crystal state of the LN or LT constituting the waveguide substrate 10 gradually changes within the ridge 50 depending on the energy of the incident laser light. It can be assumed that by maintaining this state for a predetermined time or longer, a crystal structure that allows laser light to easily pass through can be formed inside the ridge 50, thereby improving the light propagation characteristics compared to before laser irradiation.

[0071] Example

[0072] The following describes in detail an embodiment used to verify the effectiveness of the photoannealing process of the present invention. It should be noted that, unless otherwise specified, the following sequence is performed at room temperature.

[0073] (Example 1)

[0074] According to reference Figure 2 and Figure 3The manufacturing process described herein involves fabricating a bonding body. Specifically, an LN substrate 10A with a diameter of 4 inches and a thickness of 500 μm and a silicon substrate are prepared, with the silicon substrate used as a support substrate 30. Furthermore, an amorphous SiO2 film with a thickness of 1.0 μm is formed on the surface of the support substrate 30, thereby forming an intermediate layer 20.

[0075] Next, after cleaning the surface of the LN substrate 10A and the surface of the support substrate 30 (intermediate layer 20 side), the two substrates are placed into a vacuum chamber and evacuated to 10°C. -6 At approximately 100 Pa, the surfaces of both substrates were simultaneously irradiated with FAB (accelerating voltage 1 kV, Ar flow rate 27 sccm) using Ar gas for 15 seconds. Afterward, FAB irradiation on the support substrate 30 side was stopped, while FAB irradiation on the LN substrate 10A side was continued for an additional 285 seconds (total 5 minutes). As a result, a sputtered film 21 with a thickness of 1.1 nm was formed on the surface of the intermediate layer 20 side of the support substrate 30.

[0076] Next, the LN substrate 10A and the support substrate 30 are directly bonded. Specifically, the beam irradiation surfaces of the two substrates are overlapped, and the two substrates are bonded at room temperature with a pressure of 10000N for 2 minutes to obtain a bonded body.

[0077] Next, the surface of the LN substrate 10A of the resulting bond is ground to a thickness of 3.6 μm, and then laser-based ridge processing is performed to form two grooves 60 with a depth of 2 μm at 6 μm intervals on the surface of the LN substrate 10A. Afterwards, the ridge-processed bond is cut to a specified size, and the cut end faces are ground to form a ridge 50 with a length of 1.4 mm in the x-direction, a length of 8.5 mm in the z-direction, a width of 6 μm, and a height of 2 μm, serving as an optical waveguide. Figure 1 A bonding assembly with the same structure as the composite substrate 100 shown.

[0078] Next, the resulting bond is placed in a high-temperature furnace and heated from room temperature to 450°C, held at that temperature for a certain period of time, and then returned to room temperature, thereby performing thermal annealing. In the following processes, the thermally annealed bond is used as the composite substrate 100 to be photo-annealed.

[0079] Next, in Figure 9 In the characteristic evaluation system of the composite substrate 100 shown, the laser output from the laser 201 (output intensity: 150mW, wavelength: 976nm) is concentrated by the incident lens 202 and irradiated onto the composite substrate 100 (the bond after thermal annealing) to be photo-annealed. Furthermore, the position of the composite substrate 100 is finely adjusted using a worktable or similar device, thereby making the laser irradiation range 51 approximately consistent with the cross-section of the ridge 50 (see reference). Figure 4In (i), the laser light irradiating along the surface direction of the composite substrate 100 passes through the ridge 50. It should be noted that... Figure 9 In this context, the direction of laser travel within the ridge 50, i.e., the extension direction of the ridge 50 in the surface direction of the composite substrate 100, is defined as the z-axis, thus defining the axial direction of the characteristic evaluation system. This axial definition is consistent with... Figure 1 and Figure 5 The crystal axis orientations of the waveguide substrate 10 shown are different. In order to prevent reflected light from returning to the laser 201 when the laser is incident on the ridge 50, in the composite substrate 100, it is preferable that the incident angle of the laser deviates from a predetermined angle relative to the direction (z-direction) of laser propagation within the ridge 50. For example, in the composite substrate 100, the angle between the end face (the incident surface of the laser) and the side face of the ridge 50 is pre-formed to 84 degrees, such that the laser refracted at this end face propagates along the z-direction within the ridge 50. This prevents reflected light from returning to the laser 201 and ensures that the laser propagates along the z-direction within the ridge 50. Furthermore, if the incident angle of the laser relative to the end face of the ridge 50 is a predetermined angle deviating from 90 degrees (e.g., 84 degrees), the composite substrate 100 can be irradiated in any direction. However, in the following description, regardless of the direction in which the laser is tilted relative to the end face of the ridge 50, if the laser irradiating the composite substrate 100 in its irradiation direction can propagate along the extension direction of the ridge 50, then the irradiation direction is referred to as the surface direction of the composite substrate 100.

[0080] As described above, when the laser is incident on the ridge 50, the laser light exiting from the opposite side of the ridge 50 is focused using the exit lens 203 and input into the measuring device 204. The intensity of the laser light received in the measuring device 204 is continuously measured. As a result, a measured value of 63.4 mW was obtained at the beginning of the measurement. Furthermore, the measured value gradually changed as the measurement time progressed, rising to 65.8 mW after 4 minutes. It should be noted that almost no change in the measured value was observed thereafter.

[0081] (Example 2)

[0082] The bond obtained using the same method as in Example 1 was placed in a high-temperature furnace and heated from room temperature to a temperature lower than that in Example 1 (300°C). This temperature was maintained for a certain period and then returned to room temperature, thereby performing thermal annealing. In the following processes, this thermally annealed bond was used as the composite substrate 100 to be photo-annealed.

[0083] Then, similarly to Example 1, in Figure 9In the characteristic evaluation system shown, the laser output from laser 201 (output intensity: 150mW, wavelength: 976nm) is focused using incident lens 202, so that its irradiation range 51 is approximately consistent with the cross-section of ridge 50, allowing the laser to pass through ridge 50. Furthermore, the laser output from the opposite side of ridge 50 is focused using exit lens 203 and input into measuring device 204, where the intensity of the laser received is continuously measured. As a result, a measured value of 34.6mW was obtained at the beginning of the measurement. Conversely, the measured value gradually changed over time, rising to 34.85mW after 4.5 minutes. It should be noted that thereafter, almost no change in the measured value was observed.

[0084] Based on Example 2 described above, it can be confirmed that, compared with Example 1, the improvement effect of light propagation characteristics brought about by subsequent photo-annealing is lower when the thermal annealing temperature is lower.

[0085] (Example 3)

[0086] The bond obtained using the same method as in Examples 1 and 2 is placed in a high-temperature furnace and heated from room temperature to 450°C, held at that temperature for a certain period of time, and then returned to room temperature, thereby performing thermal annealing. In the following processes, the thermally annealed bond is used as the composite substrate 100 to be photo-annealed.

[0087] Then, similarly to Examples 1 and 2, in Figure 9 In the characteristic evaluation system shown, the laser output from laser 201 (output intensity: 100mW, wavelength: 976nm) is concentrated using incident lens 202, so that its irradiation range 51 is approximately consistent with the cross-section of ridge 50, allowing the laser to pass through ridge 50. Furthermore, the laser output from the opposite side of ridge 50 is concentrated using exit lens 203 and input into measuring device 204, where the intensity of the laser received is continuously measured. As a result, a measured value of 41.2mW is obtained at the beginning of the measurement. Conversely, as the measurement time progresses, the measured value gradually changes, rising to 41.6mW after 4 minutes and to 41.65mW after 6 minutes.

[0088] Based on Example 3 described above, it can be confirmed that: compared with Example 1, when the laser intensity is low, the improvement effect of optical annealing on optical propagation characteristics is low, and the time required for the improvement effect to reach its peak is long.

[0089] (Example 4)

[0090] Regarding the composite substrate 100 used in Example 3, make Figure 9In the characteristic evaluation system shown, the laser output intensity changes from 100mW to 200mW, and measurements based on measuring device 204 continue. At this point, a measured value of 85.5mW is obtained immediately after the laser output intensity changes. In contrast, even after the measurement time has elapsed, the measured value changes little, rising slightly to 85.55mW after 5 minutes.

[0091] Then, the laser output intensity was reduced from 200mW to 150mW, and measurements were continued based on the measuring device 204. At this point, a measured value of 64.1mW was obtained, and the measured value did not change even after 5 minutes.

[0092] Then, the laser output intensity was reduced from 150mW to 100mW, and measurements were continued based on the measuring device 204. At this point, a measured value of 43.2mW was obtained, and the measured value did not change even after 5 minutes.

[0093] Based on Example 4 described above, it can be confirmed that when the improvement effect of the light propagation characteristics brought about by laser irradiation reaches its peak, the light propagation characteristics do not change even if the output intensity of the laser is changed thereafter.

[0094] According to the embodiments of the present invention described above, the following effects are achieved.

[0095] (1) The manufacturing method of the composite substrate 100 includes: a film forming process, forming an intermediate layer 20 containing at least one of SiO2, MgF2, and CaF2 on a support substrate 30. Figure 2 (b) In the activation process, FAB is irradiated onto the surface of the piezoelectric material substrate (LN substrate 10A) formed by using LN (or LT) as a material and the surface of the intermediate layer 20 formed on the support substrate 30, respectively. Figure 2 (c) In the sputtering process, the surface of the LN substrate 10A is further irradiated with FAB to form a sputtered film 21 containing the material of the LN substrate 10A on the surface of the intermediate layer 20. Figure 2 (d) In the bonding process, the LN substrate 10A and the intermediate layer 20 on which the sputtered film 21 is formed are bonded to obtain a bond body. Figure 3 (e)); and the photoannealing process, in which the bond is irradiated with a laser along the surface direction of the composite substrate 100 (in the process of photoannealing). Figure 4 In (i) of the above, the composite substrate 100 is formed by using a bond that has been irradiated with a laser during the photo-annealing process. Thus, even if the piezoelectric material substrate is directly bonded to the intermediate layer 20 without setting other layers, it is possible to achieve a method for manufacturing a composite substrate 100 that improves the bonding strength between the intermediate layer 20 and the piezoelectric material substrate provided on the support substrate 30 and has good light propagation characteristics.

[0096] (2) The manufacturing method of the composite substrate 110 includes: an activation step, wherein the surface of the LN substrate 10A formed by using LN (or LT) as a material and the surface of the support substrate 30 containing SiO2, MgF2 or CaF2 are respectively irradiated with FAB (FeCl2). Figure 6 (b) In the sputtering process, the surface of the LN substrate 10A is further irradiated with FAB to form a sputtered film 21 made of the material of the LN substrate 10A on the surface of the support substrate 30. Figure 6 (c) In the bonding process, the LN substrate 10A and the support substrate 30 on which the sputtered film 21 is formed are bonded to obtain a bonded body. Figure 7 (d)); and the photo-annealing process, in which the bond is irradiated with a laser along the surface direction of the composite substrate 110 ( Figure 8 In step (h), a composite substrate 110 is formed using a bond that has been irradiated with a laser during the photo-annealing process. Thus, even when the piezoelectric material substrate is directly bonded to the support substrate 30 without the presence of other layers, a method for manufacturing a composite substrate 110 that improves the bonding strength between the support substrate 30 and the piezoelectric material substrate and has good light propagation characteristics can be achieved.

[0097] (3) The manufacturing method of composite substrates 100 and 110 further includes: a heat annealing process of heating the bond to a specified temperature. Figure 4 (h) in Figure 8 (g)). In the laser irradiation annealing process, the bond that has been heated to a specified temperature by the thermal annealing process can be irradiated with a laser. Accordingly, the bonding strength between the piezoelectric material substrate and the intermediate layer 20 or the support substrate 30 can be further improved, and thus, it is possible to reliably prevent the bond from peeling off in the sheet metal processing or ridge processing processes performed before the laser annealing process.

[0098] (4) The manufacturing method of composite substrates 100 and 110 further includes a ridge processing step of forming a ridge 50 on the LN substrate 10A of the bonding body. In the laser irradiation annealing step, it is preferable to set an irradiation range 51 corresponding to the ridge 50 and irradiate the irradiation range 51 with laser. Accordingly, in composite substrates 100 and 110, a ridge 50 that can be used as an optical waveguide with good light propagation characteristics can be obtained.

[0099] (5) In the laser annealing process, it is preferable to irradiate the bonding body used for manufacturing the composite substrates 100 and 110 with a laser for 4 minutes or more. In addition, it is preferable to irradiate the bonding body with a laser output power of 100mW or more. Accordingly, good light propagation characteristics can be reliably obtained in the composite substrates 100 and 110.

[0100] It should be noted that the present invention is not limited to the above-described embodiments, and can be implemented using any constituent elements without departing from its spirit.

[0101] The above-described embodiments and modifications are merely examples, and are acceptable as long as they do not impair the features of the invention. The present invention is not limited to these embodiments. Furthermore, while various embodiments and modifications have been described above, the present invention is not limited to these. Other solutions considered within the scope of the technical concept of the present invention are also included within the scope of the present invention.

[0102] Explanation of reference numerals in the attached figures

[0103] 10: Waveguide substrate

[0104] 10A: LN substrate

[0105] 11: First floor

[0106] 12: Second layer

[0107] 13: Third layer

[0108] 20: Intermediate layer

[0109] 21: Sputtered film

[0110] 30: Support substrate

[0111] 40: Joint Interface

[0112] 50: Spine

[0113] 51: Irradiation range

[0114] 60: Ditch

[0115] 100, 110: Composite substrate

[0116] 201: Laser

[0117] 202: Incident lens

[0118] 203: Exit Lens

[0119] 204: Measuring instrument

Claims

1. A method for manufacturing a composite substrate, comprising the following steps: An intermediate layer comprising at least one of SiO2, MgF2, and CaF2 is formed on a support substrate; High-speed atomic beams were irradiated onto the surface of a piezoelectric material substrate formed by using LN or LT as a material and the surface of the intermediate layer formed on the support substrate, respectively. The surface of the piezoelectric material substrate is further irradiated with the high-speed atomic beam to form a sputtered film containing the material of the piezoelectric material substrate on the surface of the intermediate layer; The piezoelectric material substrate and the intermediate layer on which the sputtered film is formed are bonded together to obtain a bonded body; and A laser is irradiated along the surface direction of the composite substrate in relation to the bonding body. The composite substrate is formed using the bonding body irradiated with the laser.

2. A method for manufacturing a composite substrate, comprising the following steps: High-speed atomic beams were used to irradiate the surface of a piezoelectric material substrate formed by using LN or LT as a material and the surface of a support substrate containing SiO2, MgF2 or CaF2, respectively. The surface of the piezoelectric material substrate is further irradiated with the high-speed atomic beam to form a sputtered film made of the material of the piezoelectric material substrate on the surface of the supporting substrate; The piezoelectric material substrate and the support substrate on which the sputtered film is formed are joined to obtain a bond; and A laser is irradiated along the surface direction of the composite substrate in relation to the bonding body. The composite substrate is formed using the bonding body irradiated with the laser.

3. The method for manufacturing the composite substrate according to claim 1 or 2, wherein, It also includes the step of heating the joint to a specified temperature. In the process of irradiating the laser, the laser is irradiated onto the bonded body after it has been heated to the specified temperature.

4. The method for manufacturing the composite substrate according to claim 1 or 2, wherein, It also includes the step of forming a ridge on the piezoelectric material substrate of the bonding body. In the process of irradiating the laser, an irradiation range corresponding to the ridge is set, and the laser is irradiated within the irradiation range.

5. The method for manufacturing the composite substrate according to claim 1 or 2, wherein, In the process of irradiating the laser, the joint is irradiated with the laser for more than 4 minutes.

6. The method for manufacturing the composite substrate according to claim 1 or 2, wherein, In the process of irradiating the laser, the joint is irradiated with an output power of 100mW or more.

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