Composite substrate and method of manufacturing composite substrate

Abstract

To provide a composition substrate which has superior reflection characteristics on a wavelength conversion layer boundary surface.SOLUTION: A composite substrate has a wavelength conversion layer which converts incident light into light having a different wavelength, and a multilayer film arranged adjacently to the wavelength conversion layer, wherein the multilayer film includes a plurality of refractive index layers, a region where the presence amount of inert gas atoms is equal to 0.5 at.% or larger is formed at a thickness-directional end part of the wavelength conversion layer on the side where the multilayer film is arranged, and the presence amount of inert gas atoms of a first refractive index layer, located closest to the wavelength conversion layer, of the multilayer film is less than 0.5 at.%.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a composite substrate and a method for manufacturing the composite substrate.

Background Art

[0002] Solid-state lasers capable of outputting short-pulse light are widely used. Lasers with very high optical output at shorter pulse widths are expected to be applied in various fields such as sensing, precision machining, and medicine. As such a laser, for example, as disclosed in Patent Document 1, a laser structure in which a semiconductor laser, a solid-state laser gain medium layer that can function as a wavelength conversion layer, and a saturable absorber are combined has been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above laser structure, the reflection characteristics of light at the wavelength conversion layer interface can greatly affect the performance of the laser.

[0005] The present invention has been made in view of the above, and its main object is to provide a composite substrate excellent in reflection characteristics at the wavelength conversion layer interface.

Means for Solving the Problems

[0006] 1. A composite substrate according to an embodiment of the present invention has a wavelength conversion layer that converts incident light into light with different wavelengths, and a multilayer film disposed adjacent to the wavelength conversion layer. The multilayer film includes a plurality of refractive index layers. In a thickness direction end portion on the side where the multilayer film of the wavelength conversion layer is disposed, a region where the abundance of inert gas atoms is 0.5 atomic % or more is formed. The abundance of inert gas atoms in the first refractive index layer closest to the wavelength conversion layer of the multilayer film is less than 0.5 atomic %. 2. In the composite substrate according to 1 above, the thickness direction end portion of the wavelength conversion layer may include a third layer, a second layer, and a first layer in this order from the multilayer film side. The abundance of inert gas atoms in the second layer may be greater than the abundance of inert gas atoms in the third layer. 3. In the composite substrate according to 2 above, the third layer may be an amorphous layer. 4. In the composite substrate according to any one of 1 to 3 above, the first refractive index layer may have a uniform refractive index in the thickness direction. 5. In the composite substrate according to any one of 1 to 4 above, the first refractive index layer may include an oxide containing at least one selected from tantalum, titanium, aluminum, yttrium, and lanthanum. 6. In the composite substrate according to any one of 1 to 5 above, the refractive indices of two adjacent layers included in the multilayer film may be different. 7. In the composite substrate according to any one of 1 to 6 above, the thickness of each layer included in the multilayer film may be 50 nm or more and 300 nm or less. 8. The composite substrate according to any one of 1 to 7 above may have the wavelength conversion layer, the multilayer film, and a surface emitting laser substrate in this order. 9. The composite substrate according to any one of 1 to 8 above may have the wavelength conversion layer, the multilayer film, and a saturable absorption layer in this order. 10. A composite substrate according to another embodiment of the present invention has, in this order, a surface-emitting laser substrate, a wavelength conversion layer that converts incident light into light having different wavelengths, and a saturable absorption layer. At least one of between the surface-emitting laser substrate and the wavelength conversion layer and between the saturable absorption layer and the wavelength conversion layer has a multilayer film disposed adjacent to the wavelength conversion layer. The multilayer film includes a plurality of refractive index layers. In the thickness direction end portion on the side where the multilayer film of the wavelength conversion layer is disposed, a region where the abundance of inert gas atoms is 0.5 atomic % or more is formed. The abundance of inert gas atoms in the first refractive index layer closest to the wavelength conversion layer of the multilayer film is less than 0.5 atomic %. 11. A laser structure according to an embodiment of the present invention includes the composite substrate according to any one of 1 to 10 above.

[0007] 12. A method for manufacturing a composite substrate according to an embodiment of the present invention is a method for manufacturing the composite substrate according to any one of 1 to 10 above, including preparing a stacked structure of a plurality of refractive index layers, performing an activation treatment on each of the surface of the wavelength conversion material substrate and the surface of the stacked structure, performing a sputtering treatment on the surface of the wavelength conversion material substrate to form a deposited layer containing components constituting the wavelength conversion material substrate on the surface of the stacked structure, and bonding the stacked structure and the wavelength conversion material substrate, in this order. 13. In the method for manufacturing a composite substrate according to 12 above, the time of the sputtering treatment may be 3 minutes to 10 minutes.

Advantages of the Invention

[0008] According to an embodiment of the present invention, a composite substrate excellent in reflection characteristics at the wavelength conversion layer interface can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. For the sake of clarity in the explanation, the drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the embodiments, but this is merely an example and does not limit the interpretation of the present invention. Also, for the drawings, the same or equivalent elements may be given the same reference numerals, and duplicate explanations may be omitted.

[0011] [Composite Substrate] FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a composite substrate according to one embodiment of the present invention. For ease of viewing the figure, the hatching of some members is omitted in FIG. 1.

[0012] The composite substrate 100 has a first main surface 1 and a second main surface 2 facing each other, a wavelength conversion layer 10 that converts incident light into light of different wavelengths, a first multilayer film 21 disposed adjacent to the first main surface 1 of the wavelength conversion layer 10, a second multilayer film 22 disposed adjacent to the second main surface 2 of the wavelength conversion layer 10, a substrate 30 disposed on the first multilayer film 21 side of the wavelength conversion layer 10, and a functional layer 40 disposed on the second multilayer film 22 side of the wavelength conversion layer 10.

[0013] The composite substrate 100 can be applied to, for example, a laser element. The substrate 30 is, for example, a substrate that constitutes a surface-emitting laser (for example, a vertical cavity surface-emitting laser (VCSEL), a vertical external cavity surface-emitting laser (VECSEL)). For example, the wavelength conversion layer 10 can convert the first wavelength of the laser light incident from the first main surface 1 side to the second wavelength. Although not shown, a resonator structure portion may be provided on the substrate 30.

[0014] As the substrate that constitutes the surface-emitting laser, for example, a gallium arsenide substrate, an indium phosphide substrate, or a gallium nitride substrate is used. The thickness of the substrate that constitutes the surface-emitting laser is, for example, 100 μm to 1000 μm.

[0015] The wavelength conversion layer 10 is composed of any suitable wavelength conversion material that can convert the incident light into light with different wavelengths. As the material that constitutes the wavelength conversion layer 10, typically, yttrium aluminum garnet (hereinafter referred to as YAG) crystal doped with Yb 3+ (Yb:YAG), YAG crystal doped with Nd 3+ (Nd:YAG) can be mentioned. In addition, as the material that constitutes the wavelength conversion layer 10, for example, Nd:YVO 4 , Nd:YLF, Nd:glass, Yb:YVO 4 , Yb:YLF, Yb:FAP, Yb:SFAP, Yb:glass, Yb:KYW, Yb:BCBF, Yb:YCOB, Yb:GdCOB, YB:YAB can be mentioned. The thickness of the wavelength conversion layer 10 is, for example, 10 μm to 600 μm.

[0016] The first multilayer film 21 is a laminate of a plurality of refractive index layers. In the illustrated example, the first multilayer film 21 includes, from the wavelength conversion layer 10 side, the first refractive index layer 21 1 , the second refractive index layer 21 2 , the third refractive index layer 21 3 , ···, and the nth refractive index layer 21 n of n layers. Specifically, the refractive index layer located closest to the wavelength conversion layer 10 side is the first refractive index layer 21 1and the refractive index layer located closest to the substrate 30 is the n-th refractive index layer 21 n Here, n is, for example, from 10 to 50, preferably from 15 to 40. The thickness of each layer included in the first multilayer film 21 is, for example, 50 nm or more and 300 nm or less.

[0017] The first multilayer film 21 includes a plurality of refractive index layers having different refractive indices, and includes a high refractive index layer having a relatively high refractive index and a low refractive index layer having a relatively low refractive index. For example, the refractive indices of two adjacent layers included in the first multilayer film 21 are different, one being a high refractive index layer and the other being a low refractive index layer. Also, for example, at least a part of the first multilayer film 21 may be configured by alternately laminating a high refractive index layer and a low refractive index layer. As a specific example, the refractive index of the second refractive index layer 21 2 may be smaller or larger than the refractive index of the first refractive index layer 21 1 and the refractive index of the third refractive index layer 21 3 In this case, the refractive index of the first refractive index layer 21 1 and the refractive index of the third refractive index layer 21 3 may be substantially the same or different.

[0018] The first multilayer film 21 is configured to transmit light of the first wavelength emitted from the substrate 30 side. Specifically, the first multilayer film 21 is configured to function as a transmission layer or an antireflection layer for light of the first wavelength. And the first multilayer film 21 is configured to suppress the emission of light of the second wavelength from the wavelength conversion layer 10 to the substrate 30 side, for example, from the viewpoint of improving light utilization efficiency. Specifically, the first multilayer film 21 is configured to function as a reflection layer for light of the second wavelength. Such functions of the first multilayer film 21 can be realized, for example, by adjusting the number of refractive index layers (n above) constituting the first multilayer film 21, the thickness of each refractive index layer, and the refractive index of each layer refractive index.

[0019] The laser light incident from the side of the first main surface 1 (substrate 30) can be emitted from the side of the second main surface 2. For example, the light of the second wavelength converted by the wavelength conversion layer 10 can be transmitted through the functional layer 40 and emitted. The functional layer 40 can function as, for example, a saturable absorption layer. In this case, the functional layer (saturable absorption layer) 40 typically contains Cr 4+ -doped YAG crystal (Cr:YAG), V 3+ -doped YAG crystal (V:YAG), or the like. The thickness of the functional layer (saturable absorption layer) 40 is, for example, 10 μm to 600 μm.

[0020] The second multilayer film 22 is a laminate of a plurality of refractive index layers. In the illustrated example, the second multilayer film 22 includes, from the side of the wavelength conversion layer 10, the first refractive index layer 22 1 , the second refractive index layer 22 2 , the third refractive index layer 22 3 , ···, and the nth refractive index layer 22 n . Specifically, the layer located closest to the wavelength conversion layer 10 is the first refractive index layer 22 1 , and the layer located closest to the functional layer 40 is the nth refractive index layer 22 n . n is, for example, 10 to 50, preferably 15 to 40. The thickness of each refractive index layer included in the second multilayer film 22 is, for example, 50 nm or more and 300 nm or less.

[0021] The second multilayer film 22 includes a plurality of refractive index layers having different refractive indices, and includes a high refractive index layer having a relatively high refractive index and a low refractive index layer having a relatively low refractive index. For example, the refractive indices of two adjacent layers included in the second multilayer film 22 are different, with one being a high refractive index layer and the other being a low refractive index layer. Also, for example, at least a part of the second multilayer film 22 can be configured by alternately laminating a high refractive index layer and a low refractive index layer. As a specific example, the refractive index of the second layer 22 2 can be smaller or larger than the refractive index of the first refractive index layer 22 1 and the refractive index of the third refractive index layer 22 3 . In this case, the refractive index of the first refractive index layer 22 1 and the refractive index of the third refractive index layer 22 3The refractive index may be substantially the same or different.

[0022] The second multilayer film 22 is configured to transmit the light of the second wavelength emitted from the wavelength conversion layer 10. Specifically, the second multilayer film 22 is configured to function as a transmission layer or an antireflection layer for the light of the second wavelength. And the second multilayer film 22 is configured to suppress the emission of the light of the first wavelength from the wavelength conversion layer 10 toward the functional layer 40 side, for example, from the viewpoint of improving the light utilization efficiency. Specifically, the second multilayer film 22 is configured to function as a reflection layer for the light of the first wavelength. Such functions of the second multilayer film 22 can be realized, for example, by adjusting the number (the above n) of the refractive index layers constituting the second multilayer film 22, the thickness of each refractive index layer, and the refractive index of each refractive index layer.

[0023] As described above, each of the first multilayer film 21 and the second multilayer film 22 (hereinafter, may be simply referred to as a multilayer film) is a laminate of a plurality of refractive index layers and can include a high refractive index layer and a low refractive index layer having different refractive indexes. The refractive index of each refractive index layer included in the multilayer film is, for example, from 1.3 to 2.4, preferably from 1.5 to 2.35. Note that the refractive index can be a value measured by a spectroscopic ellipsometer or a spectrophotometer. The refractive index of the high refractive index layer is relatively higher than the refractive index of the low refractive index layer. Specifically, the refractive index of the material constituting the high refractive index layer is higher than the refractive index of the material constituting the low refractive index layer. The refractive index of the low refractive index layer is, for example, from 1.3 to 1.8. The refractive index of the high refractive index layer is, for example, from 1.55 to 2.4.

[0024] The plurality of low refractive index layers that can be included in the multilayer film may each have the same configuration (for example, material, thickness), or may have different configurations from each other. Similarly, the plurality of high refractive index layers that can be included in the multilayer film may each have the same configuration (for example, material, thickness), or may have different configurations from each other.

[0025] Typically, a dielectric material is used as the material constituting each refractive index layer included in the multilayer film. Specific examples of the material constituting each refractive index layer included in the multilayer film include silicon oxide, tantalum oxide, titanium oxide, aluminum oxide, yttrium oxide, zirconium oxide, hafnium oxide, and lanthanum oxide. These may be used alone or in combination of two or more (for example, as a composite oxide). Specifically, the refractive index layer may be composed of an oxide containing at least one selected from silicon, tantalum, titanium, aluminum, yttrium, zirconium, hafnium, and lanthanum.

[0026] The first refractive index layer included in the multilayer film preferably contains an oxide containing at least one selected from tantalum, titanium, aluminum, yttrium, and lanthanum. According to such a first refractive index layer, the adhesion between the multilayer film and the wavelength conversion layer 10 can be excellent.

[0027] Each refractive index layer included in the multilayer film can be formed by any suitable method. Each refractive index layer included in the multilayer film can be formed, for example, by physical vapor deposition such as sputtering, ion beam assisted deposition (IAD), chemical vapor deposition, or atomic layer deposition (ALD) method.

[0028] Inert gas atoms are present at the end portion (hereinafter, may be referred to as the end portion in the thickness direction) 10a on the side where the multilayer film of the wavelength conversion layer 10 is disposed. Here, the end portion in the thickness direction means a portion having a certain thickness. Representative examples of the inert gas atoms include argon and xenon. The region where the inert gas atoms are present and formed at the end portion 10a in the thickness direction of the wavelength conversion layer 10 can be formed over the entire surface of the wavelength conversion layer 10. For example, in the wavelength conversion layer 10, a layer in which inert gas atoms are present is formed at the end portion 10a in the thickness direction. The abundance of the inert gas atoms in the region (layer) where the inert gas atoms are present is, for example, 0.5 atomic% or more and 10 atomic% or less, and may be 0.7 atomic% or more.

[0029] On the other hand, it is preferable that substantially no inert gas atoms are present in the central portion 10b in the thickness direction of the wavelength conversion layer 10. The abundance of inert gas atoms in the central portion 10b in the thickness direction of the wavelength conversion layer 10 is, for example, less than 0.5 atomic %, and may be 0.4 atomic % or less.

[0030] FIG. 2 is a schematic partial enlarged cross-sectional view showing an example of the state of the end portion in the thickness direction of the wavelength conversion layer. In the end portion 10a in the thickness direction of the wavelength conversion layer 10, a third layer 13, a second layer 12, and a first layer 11 are formed in this order from the multilayer film 21 (22) side. For example, the third layer 13 can be an amorphous layer. The first layer 11 can be a crystal layer. The second layer 12 may be an amorphous layer, a crystal layer, or a combination thereof. The second layer 12 and the third layer 13 may contain the constituent atoms of the first layer 11.

[0031] The inert gas atoms can mainly exist in the second layer 12. The inert gas atoms may exist in the third layer 13 or may not substantially exist in the third layer 13. For example, the abundance of inert gas atoms in the second layer 12 is greater than the abundance of inert gas atoms in the third layer 13. The abundance of inert gas atoms in the second layer 12 is, for example, 0.5 atomic % or more and 10 atomic % or less, preferably 0.7 atomic % or more and 4 atomic % or less. The lower limit value of the abundance of inert gas atoms in the third layer 13 may be 0.2 atomic %, preferably 0 atomic %. The upper limit value of the abundance of inert gas atoms in the third layer 13 may be 10 atomic %, preferably 3 atomic %. The second layer 12 and / or the third layer 13 may contain Fe and Cr.

[0032] The thickness of the second layer 12 is, for example, 0.2 nm or more, and may be 0.4 nm or more. On the other hand, the thickness of the second layer 12 is, for example, 10 nm or less, preferably 5 nm or less. The thickness of the third layer 13 is, for example, 0.2 nm or more, and may be 0.3 nm or more. On the other hand, the thickness of the third layer 13 is, for example, 8 nm or less, preferably 4 nm or less.

[0033] In the first refractive index layer of the multilayer film adjacent to the wavelength conversion layer 10, inert gas atoms are substantially absent, and the abundance of inert gas atoms in the first refractive index layer is, for example, less than 0.5 atomic %, and may be 0.4 atomic % or less. By having such a configuration for the first refractive index layer closest to the wavelength conversion layer 10, for example, the mixing of components constituting the wavelength conversion layer into the first refractive index layer is suppressed, and the first refractive index layer can have a uniform refractive index in its thickness direction. Specifically, in the thickness direction of the first refractive index layer, there is substantially no difference in refractive index between the wavelength conversion layer 10 side and the second refractive index layer side. By the refractive index of the first refractive index layer being uniform, for example, desired reflection characteristics can be satisfactorily achieved.

[0034] The abundance of the above-mentioned inert gas atoms can be determined, for example, by composition analysis using energy dispersive X-ray spectroscopy (EDX).

[0035] The composite substrate 100 may omit the functional layer 40 and the second multilayer film 22, or may omit the substrate 30 and the first multilayer film 21. Also, although not shown, the composite substrate 100 may further have any layer. The type, function, number, combination, arrangement, etc. of such layers can be appropriately set according to the purpose. For example, another functional layer (e.g., an optical scanner layer) may be provided on the functional layer 40 of the composite substrate 100.

[0036] The composite substrate 100 can be manufactured in any appropriate shape. In one embodiment, it can be manufactured in the form of a so-called wafer. The size of the composite substrate 100 can be appropriately set according to the purpose. For example, the diameter of the wafer is 50 mm to 150 mm. Also, for example, the diameter of the wafer is 3 inches to 6 inches.

[0037] [Manufacturing Method] The above-mentioned composite substrate can be obtained, for example, by preparing a laminated structure of a plurality of refractive index layers and bonding this laminated structure to a wavelength conversion material substrate.

[0038] Figs. 3A to 3D are diagrams showing an example of a manufacturing process of a composite substrate according to one embodiment. Fig. 3A shows a state in which n layers from the first refractive index layer 21 to the nth refractive index layer 21 that can form the first multilayer film 21 are formed on the substrate 30 in order, and an n-layer laminated structure 20 is formed on the substrate 30. 1 from the first refractive index layer 21 n to the nth refractive index layer 21 n of the n layers are formed in order on the substrate 30, showing a state in which an n-layer laminated structure 20 is formed on the substrate 30.

[0039] Next, the laminated structure 20 and the wavelength conversion material substrate 14 are directly bonded. At the time of direct bonding, the laminated structure 20 and the wavelength conversion material substrate 14 are preferably activated by any appropriate activation treatment, respectively.

[0040] Typically, the above activation treatment is performed by irradiating a neutralization beam. Preferably, a neutralization beam is generated using an apparatus such as the apparatus described in JP-A-2014-086400, and the activation treatment is performed by irradiating this beam. Specifically, as a beam source, a saddle field type high-speed atomic beam (FAB) source is used, an inert gas such as argon or xenon is introduced into the chamber, and a high voltage is applied from a DC power supply to the electrode. As a result, due to the saddle field type electric field generated between the electrode (positive electrode) and the housing (negative electrode), electrons move, and a beam of atoms and ions by the inert gas is generated. Among the beams reaching the grid, the ion beam is neutralized by the grid, so a beam of neutral atoms is emitted from the high-speed atomic beam source. The voltage during beam irradiation is preferably 0.5 kV to 2.0 kV. The current during beam irradiation is preferably 50 mA to 200 mA.

[0041] In one embodiment, the activation treatment can be performed in two steps. Fig. 3B shows a state in which a first activation treatment is performed on the surface 20a of the laminated structure 20 and the surface 14a of the wavelength conversion material substrate 14, respectively. Typically, the activation of the surface 20a of the laminated structure 20 and the activation of the surface 14a of the wavelength conversion material substrate 14 can be performed simultaneously. The time of the first activation treatment (for example, the irradiation time of the above beam) is preferably 10 seconds to 30 seconds.

[0042] Figure 3C shows the second activation process. In the second activation process, the surface 14a of the wavelength conversion material substrate 14 is further irradiated with a beam. Here, substantially no beam irradiation is performed on the laminated structure 20 side. By the second activation process, a deposition layer 15 containing components constituting the wavelength conversion material substrate 14 can be formed on the surface of the laminated structure 20. Therefore, the second activation process can be considered as a sputtering process. For example, the second activation process (sputtering process) is performed by, in the first activation process, after irradiating the laminated structure 20 and the wavelength conversion material substrate 14 with a beam, stopping the beam irradiation on the laminated structure 20 and continuing the beam irradiation on the wavelength conversion material substrate 14 for a further predetermined time. The time of the second activation process (sputtering process) (for example, the irradiation time of the beam) is, for example, 3 minutes to 10 minutes, preferably 4 minutes to 7 minutes.

[0043] The deposition layer 15 can be an amorphous layer. The thickness of the deposition layer 15 is preferably 0.2 nm to 8 nm, more preferably 0.3 nm to 4 nm. The deposition layer 15 can contain components constituting the wavelength conversion material substrate 14 as described above. Further, the deposition layer 15 can contain inert gas atoms. The deposition layer 15 can correspond to the third layer 13 of the obtained composite substrate.

[0044] After the activation process, the deposition layer 15 formed on the laminated structure 20 and the wavelength conversion material substrate 14 are brought into contact with each other and directly joined by applying pressure. Thus, the joined body (composite substrate) 102 shown in Figure 3D is obtained. The contact and pressure application are preferably performed in a vacuum atmosphere. The temperature at this time is typically room temperature. Specifically, 20°C or higher and 40°C or lower is preferable, and more preferably 25°C or higher and 30°C or lower. The pressure applied is preferably 100 N to 20000 N.

[0045] The dashed line in FIG. 3D indicates the bonding interface. The bonding interface may be located inside the wavelength conversion layer 10. And in the wavelength conversion layer 10, three layers (the first layer 11, the second layer 12, and the third layer 13) are formed in the vicinity of the bonding interface. The first layer 11 substantially does not contain, for example, the inert gas atoms used in the activation treatment. The second layer 12 is located closer to the first multilayer film 21 than the first layer 11 and may contain inert gas atoms. The third layer 13 is in contact with the first multilayer film 21 and may or may not contain inert gas atoms. The abundance of the inert gas in these layers is as described above. The first layer 11 may be composed of a crystal of the wavelength conversion material. The third layer 13 may be an amorphous layer in which the wavelength conversion material is amorphous. The second layer 12 may be composed of a crystal of the wavelength conversion material, may be composed of an amorphous body in which the wavelength conversion material is amorphous, or may be a combination of these.

[0046] By positioning the bonding interface inside the wavelength conversion layer 10, the influence of the activation treatment on the laminated structure 20, which may require high-precision control of the refractive index, can be made extremely low. Specifically, in the first refractive index layer of the multilayer film (the outermost layer of the laminated structure 20), the inert gas atoms used in the activation treatment are substantially absent, and the mixing of the wavelength conversion material due to the activation treatment and the generation of an amorphous structure (for example, an amorphous region containing inert gas atoms) by the activation treatment can be suppressed. As a result, the first refractive index layer may have a desired refractive index, and for example, the desired reflection characteristics of the entire multilayer film can be satisfied well. In addition, the mixing of impurities (for example, Fe, Cr, etc. constituting the jigs and pedestal parts of the activation treatment apparatus) into the first refractive index layer of the multilayer film (the outermost layer of the laminated structure 20) can be suppressed. The impurities can affect, for example, the transmittance of the multilayer film. Furthermore, the generation of an amorphous layer accompanying bonding can be suppressed. Specifically, the thickness of the amorphous layer generated accompanying bonding can be reduced.

[0047] After direct bonding, the bonded body 102 may be subjected to an annealing process. Specifically, the bonded body 102 can be heated. According to the annealing process, inert gas atoms and the above impurities can be diffused and volatilized. Also, crystallization of the amorphous state can be expected by the annealing process, and for example, further improvement of the reflection characteristics can be expected. The temperature (heating temperature) of the annealing process is, for example, 300°C to 450°C.

[0048] At the time of bonding, the surfaces of the laminated structure 20 and the wavelength conversion material substrate 14 are preferably flat surfaces. Specifically, the arithmetic mean roughness Ra of the surfaces of the laminated structure 20 and the wavelength conversion material substrate 14 is preferably 5 nm or less, more preferably 2 nm or less, still more preferably 1 nm or less, and particularly preferably 0.3 nm or less. Examples of the method for planarizing the surface include mirror polishing by chemical mechanical polishing (CMP), lap polishing, etc.

[0049] At the time of the above film formation and bonding, for example, in order to remove residues of the abrasive, it is preferable to clean the surfaces of each layer. Examples of the cleaning method include wet cleaning, dry cleaning, and scrub cleaning. Among these, scrub cleaning is preferable because it can clean simply and efficiently. As a specific example of scrub cleaning, after using a cleaning agent (for example, the Sun Wash series manufactured by Lion Corporation), a method of cleaning with a scrub cleaning machine using a solvent (for example, a mixed solution of acetone and isopropyl alcohol (IPA)) can be mentioned.

[0050] In FIG. 3, the formation of the laminated structure 20 on the substrate 30 and the manufacturing of the bonded body of the wavelength conversion layer 10 and the first multilayer film 21 are shown. Similar to the example shown in FIG. 3, by forming the laminated structure 20 on the functional layer 40 and bonding this to the wavelength conversion material substrate 14, a bonded body of the wavelength conversion layer 10 and the second multilayer film 22 can be obtained. When obtaining the composite substrate shown in FIG. 1, the lamination order of the substrate 30 and the functional layer 40 with respect to the wavelength conversion material substrate 14 is not particularly limited. Specifically, after bonding the substrate 30 to the wavelength conversion material substrate 14, the functional layer 40 may be bonded, or after bonding the functional layer 40, the substrate 30 may be bonded.

Example

[0051] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited by these examples.

[0052] [Example 1] On a substrate (GaAs substrate), a tantalum oxide (Ta 2 O 5 ) layer, a silicon oxide (SiO 2 ) layer, and an aluminum oxide (Al 2 O 3 ) layer are formed in the order and thickness shown in Table 1 to form a laminated structure of a total of 29 refractive index layers. For this laminated structure, the refractive indices of each layer of the composite substrate obtained by bonding the Yb:YAG substrate are summarized in Table 1 by the method shown in FIG. 3.

[0053] As shown in Table 1, in the first refractive index layer (tantalum oxide layer), the influence of the activation treatment (beam irradiation) is extremely low, and a desired refractive index is obtained.

[0054] [Comparative Example 1] On a substrate (GaAs substrate), a tantalum oxide (Ta 2 O 5 ) layer, a silicon oxide (SiO 2 ) layer, and an aluminum oxide (Al 2 O 3 ) layer are formed in the same manner as in Example 1 to form a laminated structure of a total of 29 refractive index layers. Then, for this laminated structure, the refractive indices of each layer of the composite substrate obtained by bonding the Yb:YAG substrate are summarized in Table 1 in the same manner as in Example 1 except that the beam irradiation to the laminated structure is not stopped during the second activation treatment in the method shown in FIG. 3.

[0055] As shown in Table 1, due to the activation treatment (beam irradiation), in the first refractive index layer (tantalum oxide layer), a layer (thickness 50 nm) having a refractive index lower than the refractive index of tantalum oxide (2.23) is formed on the Yb:YAG layer side. YAG constituent components can be confirmed in this layer (region).

[0056]

Table 1

[0057] The simulation results of the reflection characteristics of the multilayer film of Example 1 are shown in FIG. 4, and the simulation results of the reflection characteristics of the multilayer film of Comparative Example 1 are shown in FIG. 5.

[0058] Yb:YAG has an effective excitation wavelength of 935 nm to 945 nm and can convert light with a wavelength of 1030 nm. The multilayer films of Example 1 and Comparative Example 1 can transmit light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer) and suppress the emission of light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer). The multilayer film of Example 1 had a reflectance of 0.1% at a wavelength of 940 nm, while the multilayer film of Comparative Example 1 had a reflectance of 1.5% at a wavelength of 940 nm. From this, it can be said that the multilayer film of Example 1 can more effectively incident light with the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer).

[0059] (Composition analysis of Example 1) On a GaAs substrate, after sequentially depositing the 29th refractive index layer to the 2nd refractive index layer shown in Table 1 with the materials and thicknesses shown in Table 1, finally, a tantalum oxide layer (the 1st refractive index layer) with a thickness of 200 nm was deposited to form a stacked structure of 29 refractive index layers. Next, after cleaning the surface of the Yb:YAG substrate (YAG crystal) and the surface of the GaAs substrate on which the stacked structure was formed (tantalum oxide layer side), both substrates were put into a vacuum chamber and evacuated to a pressure of 10 -6 Pa, and FAB (acceleration voltage 1 kV, Ar flow rate 27 sccm) using Ar gas was simultaneously irradiated on the surfaces of both substrates for 15 seconds each. Then, the FAB irradiation on the GaAs substrate side was stopped, and the FAB irradiation on the Yb:YAG substrate side was continued for another 285 seconds. Next, the GaAs substrate and the Yb:YAG substrate were directly bonded. Specifically, the FAB irradiation surfaces of both substrates were overlapped, and the two substrates were bonded by applying a pressure of 10000 N at room temperature for 2 minutes to obtain a bonded body as shown in FIGS. 2 and 3D. Thereafter, the obtained joined body was subjected to annealing treatment. Specifically, the obtained joined body was placed in a high-temperature furnace, and in this state, the temperature in the high-temperature furnace was raised from room temperature to a temperature higher than 100 °C and held for a certain period of time, and then returned to room temperature to perform annealing.

[0060] In order to measure the content (abundance) of Ar in each layer constituting the joined body, while thinning the joined body by the FIB (focused ion beam) method, the surface of each layer was exposed, and energy-dispersive X-ray analysis (EDX) was performed. Specifically, using an atomic-resolution analytical electron microscope (manufactured by JEOL, JEM-ARM200F Dual-X) and an energy-dispersive X-ray analyzer (manufactured by JEOL, JED-2300), with an acceleration voltage of 200 kV and a beam spot size of approximately 0.2 nm Φ, analysis was performed by STEM-EDX observation. The measurement results are shown below. The content of Ar indicates the ratio of Ar atoms to all atoms present at the measurement location. · Measurement location 1 (YAG crystal corresponding to the first layer 11): 0 atomic % · Measurement location 2 (second layer 12): 2 atomic % · Measurement location 3 (third layer 13): 1 atomic % · Measurement location 4: (tantalum oxide layer corresponding to the first refractive index layer 21 1 ): 0.4 atomic %

[0061] [Example 2] On the Cr:YAG substrate, a tantalum oxide (Ta 2 O 5 ) layer, a silicon oxide (SiO 2 ) layer, and an aluminum oxide (Al 2 O 3 ) layer were formed in the order and thickness shown in Table 2 to form a laminated structure of 33 refractive index layers. For this laminated structure, the refractive indices of each layer of the composite substrate obtained by joining the Yb:YAG substrate by the method shown in Figure 3 are summarized in Table 2.

[0062]

Table 2

[0063] As shown in Table 2, in the first refractive index layer (tantalum oxide layer), the influence of the activation treatment (beam irradiation) is extremely low, and a desired refractive index can be obtained.

[0064] The simulation results of the reflection characteristics of the multilayer film of Example 2 are shown in FIG. 6.

[0065] The multilayer film of Example 2 can transmit light with a wavelength of 1030 nm emitted from the wavelength conversion layer (Yb:YAG layer) and suppress the emission of light at the effective excitation wavelength of the wavelength conversion layer (Yb:YAG layer).

Industrial Applicability

[0066] The composite substrate according to the embodiment of the present invention can be suitably used for laser elements such as for sensing, precision machining, and medical use.

Explanation of Reference Numerals

[0067] 10 Wavelength conversion layer 11 First layer 12 Second layer 13 Third layer 14 Wavelength conversion material substrate 20 Laminated structure 21 First multilayer film 22 Second multilayer film 30 Substrate 40 Functional layer 100 Composite substrate 102 Bonded body (composite substrate)

Claims

1. A wavelength conversion layer that converts incident light into light with different wavelengths, and a multilayer film disposed adjacent to the wavelength conversion layer, wherein the multilayer film includes a plurality of refractive index layers, a region having an abundance of inert gas atoms of 0.5 atomic % or more is formed at a thickness direction end portion on the side where the multilayer film of the wavelength conversion layer is disposed, the abundance of inert gas atoms in the first refractive index layer closest to the wavelength conversion layer of the multilayer film is less than 0.5 atomic %, A composite substrate.

2. The thickness direction end portion of the wavelength conversion layer includes a third layer, a second layer, and a first layer in this order from the multilayer film side, and the abundance of inert gas atoms in the second layer is greater than the abundance of inert gas atoms in the third layer. The composite substrate according to claim 1.

3. The third layer is an amorphous layer. The composite substrate according to claim 2.

4. The first refractive index layer has a uniform refractive index in the thickness direction. The composite substrate according to claim 1.

5. The first refractive index layer includes an oxide containing at least one selected from tantalum, titanium, aluminum, yttrium, and lanthanum. The composite substrate according to claim 1.

6. The refractive indices of two adjacent layers included in the multilayer film are different. The composite substrate according to claim 1.

7. The thickness of each layer included in the multilayer film is 50 nm or more and 300 nm or less. The composite substrate according to claim 1.

8. The composite substrate according to claim 1, having the wavelength conversion layer, the multilayer film, and a surface emitting laser substrate in this order.

9. The composite substrate according to claim 1, having the wavelength conversion layer, the multilayer film, and a saturable absorption layer in this order.

10. A surface emitting laser substrate, a wavelength conversion layer that converts incident light into light with different wavelengths, and a saturable absorption layer, in this order, and having a multilayer film disposed adjacent to the wavelength conversion layer between at least one of between the surface emitting laser substrate and the wavelength conversion layer and between the saturable absorption layer and the wavelength conversion layer, wherein the multilayer film includes a plurality of refractive index layers, a region having an abundance of inert gas atoms of 0.5 atomic % or more is formed at a thickness direction end portion on the side where the multilayer film of the wavelength conversion layer is disposed, the abundance of inert gas atoms in the first refractive index layer closest to the wavelength conversion layer of the multilayer film is less than 0.5 atomic %, A composite substrate.

11. A laser structure including the composite substrate according to claim 1.

12. The method for manufacturing a composite substrate according to claim 1, comprising: preparing a laminated structure of a plurality of refractive index layers; performing an activation treatment on each of the surface of the wavelength conversion material substrate and the surface of the laminated structure; performing a sputtering treatment on the surface of the wavelength conversion material substrate to form a deposition layer containing components constituting the wavelength conversion material substrate on the surface of the laminated structure; and bonding the laminated structure and the wavelength conversion material substrate, in this order, The method for manufacturing a composite substrate.

13. The method for manufacturing a composite substrate according to claim 12, wherein the time of the sputtering treatment is 3 minutes to 10 minutes.

Images