Optical device and method for manufacturing optical device

Abstract

The purpose of the present disclosure is to provide a method for manufacturing an optical device having a reflective film that can be formed by one film-forming apparatus. This optical device comprises: an optical element; and a reflective film provided to an end surface of the optical element, said end surface facing the optical waveguide direction. The reflective film has: a first layer film that is provided on the end surface of the optical element and that transmits light; and a second layer film that is provided on the first layer film and that reflects light. The first layer film is an oxide or a nitride of a metal, and the second layer film is the metal.

Description

Optical device and method for manufacturing an optical device

[0001] This disclosure relates to an optical device provided with a reflective film and a method for manufacturing the same.

[0002] Non-patent document 1 discloses a quantum cascade laser in which a high-reflective (HR) coating is applied to reduce losses in the cavity mirror. In this laser, SiO is applied to the rear end face of the laser. ２ Ti, which improves the adhesion of Au, and Au are stacked in this order. High reflectivity can be ensured by Au, and SiO ２ By inserting this, the laser body and the Ti / Au layer can be insulated.

[0003] The formula for calculating the reflectance of a multilayer film is disclosed in Patent Document 1.

[0004] Note that Al at a wavelength of 9 μm ２ O ３ , TiO ２ The complex refractive index of AlN is disclosed in Non-Patent Document 2.

[0005] The complex refractive indices of Al, Ti, and Au at a wavelength of 9 μm are disclosed in Non-Patent Document 3.

[0006] Furthermore, Ta at a wavelength of 9 μm ２ O ５ The complex refractive index is disclosed in Non-Patent Document 4.

[0007] The complex refractive index of Ta at a wavelength of 9 μm is disclosed in Non-Patent Document 5.

[0008] Japanese Patent Publication No. 2010-219568

[0009] J. S. Yu et. al., “High-performance continuous-wave operation of λ~4.6μm quantum-cascade lasers above room temperature”, IEEE J. Quantum Electron., vol. 44, no. 8, pp. 747-754, 2008. J. Kischkat et. al., “Mid-infrared optical properties of thin films of aluminum oxide, titanium dioxide, silicon dioxide, aluminum nitride, and silicon nitride”, Appl. Opt., vol. 51, no. 28, pp. 6789-6798, 2012. A.D. Rakic et. al., “Optical properties of metallic films for vertical-cavity optoelectronic devices”, Appl. Opt., vol. 37, no. 22, pp. 5271-5283, 1998. E.Franke et. al., “Dielectric function of amorphous tantalum oxide from the far infrared to the deep ultraviolet spectral region measured by spectroscopic ellipsometry”, J. Appl. Phys., vol. 88, no. 9, pp. 5166-5174, 2000. M. A. Ordal et. al., “Optical properties of Al, Fe, Ti, W, and Mo at submillimeter wavelengths”, Appl. Opt., vol. 27, no. 6, pp. 1203-1209, 1988.

[0010] In the method of Non-Patent Document 1, SiO ２Since the reflective film was deposited using the PECVD (Plasma Enhanced Chemical Vapor Deposition) method and the Ti / Au film was deposited using the EB (Electron Beam Evaporation) method, two deposition systems were required to produce the reflective film.

[0011] This disclosure aims to provide an optical device having a reflective film that can be formed using a single film deposition apparatus in order to solve the above-mentioned problems.

[0012] This disclosure aims to provide a method for manufacturing an optical device having a reflective film that can be formed using a single film deposition apparatus, in order to solve the above-mentioned problems.

[0013] Preferably, an optical device comprises an optical element and a reflective film provided on an end face of the optical element facing the direction of light guidance, wherein the reflective film has a first layer film provided on the end face of the optical element that transmits light, and a second layer film provided on the first layer film that reflects light, the first layer film being a metal oxide or nitride, and the second layer film being the metal.

[0014] In the optical device of this disclosure, a first layer film and a second layer film, which is the outermost surface, are laminated in this order on the rear end face of a semiconductor laminate. The first layer film is a metal oxide or nitride, and the second layer film is the elemental metal. A reactive sputtering apparatus is used to manufacture the optical device. When the first layer film is a metal oxide, oxygen is used as the raw material gas, and when the first layer film is a metal nitride, nitrogen is used as the raw material gas. The first layer film can be deposited by supplying the raw material gas to the sample chamber in the reactive sputtering apparatus and sputtering a sputtering target made of the metal. The second layer film can be deposited by stopping the supply of the raw material gas and sputtering the sputtering target. This makes it possible to provide an optical device having a reflective film that can be deposited with a single film deposition apparatus, and a method for manufacturing the same.

[0015] This is a perspective view of the optical device according to Embodiment 1. This is a cross-sectional view taken along the line ya-yb in Figure 1. This is an enlarged cross-sectional view of the reflective film according to Embodiment 1. This is the result of calculating the reflectance of the reflective film according to Embodiment 1 as a function of the film thickness of the second layer. This is the result of calculating the reflectance of the reflective film according to the comparative example as a function of the film thickness of the third layer. This is a diagram showing the method for manufacturing the optical device according to Embodiment 1. This is a top view of the sample according to Embodiment 1. This is a cross-sectional view taken along the line xa-xb in Figure 7. This is the result of calculating the reflectance of the reflective film according to Embodiment 2 as a function of the film thickness of the second layer. This is the result of calculating the reflectance of the reflective film according to Embodiment 3 as a function of the film thickness of the second layer. This is the result of calculating the reflectance of the reflective film according to Embodiment 4 as a function of the film thickness of the second layer. This is the result of calculating the reflectance of the reflective film according to Embodiment 5 as a function of the film thickness of the second layer. This is the result of calculating the reflectance of the reflective film according to Embodiment 6 as a function of the film thickness of the second layer. This is an enlarged cross-sectional view of the reflective film according to Embodiment 7. This is the result of calculating the reflectance of the reflective film according to Embodiment 7 as a function of the thickness of the second layer film. This is an enlarged cross-sectional view of the reflective film according to Embodiment 8. This is the result of calculating the reflectance of the reflective film according to Embodiment 8 as a function of the thickness of the second layer film.

[0016] Embodiments of this disclosure will be described with reference to the drawings. The same or corresponding components are denoted by the same reference numerals, and repetition in the description may be omitted. Furthermore, the materials, dimensions, etc., of the semiconductor layer and reflective film described herein are examples only and may differ from those of actual components.

[0017] Embodiment 1 Figure 1 is a perspective view of the optical device 100 according to Embodiment 1. Here, as an example, the case in which the optical device 100 is a quantum cascade laser (QCL) will be described. However, the optical device 100 of this disclosure is not limited to a quantum cascade laser, and may also be a semiconductor laser device such as a laser diode (LD).

[0018] In this figure, the direction of the laser beam's guidance is defined as the positive direction of the y-axis. The thickness direction of the semiconductor layer is defined as the direction of the z-axis.

[0019] The optical device 100 has, in order, an n-type InP buffer layer 3 (film thickness 1.0 μm), an n-type GaInAs photoconfinement layer 4 (film thickness 230 nm), a core region 5 consisting of 30 to 40 stages, an n-type GaInAs photoconfinement layer 6 (film thickness 230 nm), an n-type InP cladding layer 7 (film thickness 3.5 μm), and an n-type GaInAs contact layer 8 (film thickness 500 nm), all stacked on an n-type InP substrate 2.

[0020] Furthermore, on the surface of the buffer layer 3, current blocking layers 10 are provided on both sides from the light confinement layer 4 to the contact layer 8.

[0021] Core region 5 has a multi-quantum well (MQW) structure in which 30 to 40 stages, each consisting of alternating GaInAs quantum well layers and AlInAs barrier layers, are stacked. Mid-infrared light of approximately 3 to 24 μm is emitted by subband transitions in the quantum well structure.

[0022] Furthermore, the number of stages constituting the core region 5 is not limited to 30 to 40; it can be adjusted as appropriate depending on the desired laser characteristics.

[0023] An n-type second electrode 9 is provided on the contact layer 8. An n-type first electrode 1 is provided on the back surface of the substrate 2. When the optical device 100 is in operation, the first electrode 1 is negatively biased and the second electrode 9 is positively biased. During operation, a voltage is applied to the first electrode 1 and the second electrode 9, injecting current into the optical device 100 and causing the laser to oscillate.

[0024] Hereafter, the semiconductor laminate 12 will refer to the substrate 2, the buffer layers 3 to the contact layer 8 sequentially stacked on the surface of the substrate 2, the current blocking layer 10, the first electrode 1, and the second electrode 9. However, the semiconductor laminate 12 in the optical device 100 of this disclosure only needs to include an active layer that generates and guides laser light. In a quantum cascade laser, the active layer is the core region 5, but the active layer does not necessarily have to be a quantum cascade laser structure.

[0025] Figure 2 is a cross-sectional view taken along the line ya-yb of FIG. 1. A reflective film 11 is provided on the rear end surface of the semiconductor laminate 12. Here, the rear end surface means the end surface opposite to the laser light emission surface.

[0026] Figure 3 is an enlarged cross-sectional view of the reflective film 11 according to Embodiment 1. The reflective film 11 has a first layer film 13, a second layer film 14, and a third layer film 15 laminated in this order on the rear end surface of the semiconductor laminate 12. In the present embodiment, the first layer film 13 is Ta with a film thickness of 450 nm ２ O ５ , the second layer film 14 is Ta, and the third layer film 15 is Ta with a film thickness of 100 nm ２ O ５ .

[0027] The first layer film 13 is responsible for insulating the semiconductor laminate 12 from the second layer film 14 which is a metal. The first layer film 13 is an electrical insulator and is preferably a material with a high transmittance with respect to the wavelength of the laser light. For example, a metal oxide can be preferably used. In the present embodiment, Ta ２ O ５ is used as the first layer film 13.

[0028] The second layer film 14 is responsible for reflecting the laser light. The second layer film 14 is a simple substance of the metal contained in the metal oxide of the first layer film 13. In the present embodiment, Ta is used as the second layer film 14.

[0029] The third layer film 15 plays a role of preventing the solder from creeping when the optical device 100 is joined to the submount. Generally, when the optical device 100 is joined to the submount, the front surface of the submount and the back surface of the substrate 2 are joined by solder such as AuSn provided on the surface of the submount. At this time, if the outermost surface of the reflective film 11 is the metal contained in the solder (Au in the case of AuSn solder), the wettability of the solder with respect to the outermost surface becomes high. As a result, a problem occurs in that the solder creeps onto the surface of the reflective film 11.

[0030] From the viewpoint of preventing this defect, it is preferable that the third layer 15 is made of a material that does not contain the metal (Au in the case of AuSn solder) used in the solder used to join the optical device 100 and the submount. By using, for example, a metal oxide as the third layer 15, the wettability of the solder can be reduced and creep can be prevented. As for the third layer 15 in this embodiment, Ta is used, the same as the first layer 13. ２ O ５ This is used. The third layer 15 may be any metal other than the metal contained in the solder.

[0031] <Calculation Results of Reflectance> The following section explains the results of the calculation of the reflectance of the reflective film 11. For the calculation, the effective refractive index of the semiconductor laminate 12 was set to nc. The complex refractive index of the first layer film 13 was set to n1. ＊ The film thickness was defined as d1. Similarly, the complex refractive index of the second layer 14 was defined as n2. ＊ Let the film thickness be d2, and the complex refractive index of the third layer 15 be n3. ＊ The film thickness was defined as d3.

[0032] Figure 4 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 1 as a function of the film thickness d2 of the second layer film 14. As an example, the reflectance at a wavelength of 9 μm was calculated. However, the effective refractive index of the semiconductor laminate 12 at a wavelength of 9 μm was set to nc = 3.15452. Also, based on Non-Patent Literature 4, Ta ２ O ５ n1 is the complex refractive index at a wavelength of 9 μm. ＊ = n3 ＊ = 1.50333 + i0.00000, where i is the imaginary unit. Also, based on Non-Patent Document 5, the complex refractive index of Ta at a wavelength of 9 μm is given by n² ＊ = 10.68374 + i48.47897. Note that there is a relationship between the complex permittivity and the complex refractive index described in Non-Patent Document 3.

[0033] Furthermore, in calculating the reflectance, we used equation (1), which is the formula for calculating the reflectance R of a multilayer film, based on Patent Document 1.

[0034]

[0035] Naor ＊This is the complex amplitude reflectance of a multilayer film, obtained from the characteristic matrix of the multilayer film.

[0036] From Figure 4, the reflectance shows a saturation tendency in the region where the film thickness d2 of Ta is 50 nm or more, reaching 96% or more. This reflectance is higher than the reflectance calculated later based on Non-Patent Literature 1, indicating that the reflective properties of the reflective film 11 of this disclosure are excellent. Furthermore, from the reflectance calculation results in Figure 4, it can be said that a film thickness d2 of 50 nm or more for the second layer film 14 of this disclosure is particularly preferable.

[0037] <Comparative Examples> Below, as comparative examples, we will explain the results of calculating the reflectance in the following cases: (1) when there is no reflective film 11, and (2) when the reflective film 11 described in Non-Patent Document 1 is assumed.

[0038] (1) Reflectance when the reflective film 11 is absent The reflectance R0 when the reflective film 11 is absent can be calculated using the following (Equation 2).

[0039]

[0040] If the effective refractive index of the semiconductor laminate 12 is set to nc = 3.15452, then R0 will be approximately 26.9%.

[0041] (2) In the reflective film 11 of the comparative example of reflectance when the reflective film 11 of Non-Patent Document 1 is assumed, the first layer film 13 is made of Al with a thickness of 450 nm. ２ O ３ The second layer 14 was made of Ti with a thickness of 15 nm, and the third layer 15 was made of Au.

[0042] Here, the first layer film 13 in Non-Patent Document 1 is SiO ２ However, in this comparative example, the first layer film 13 is made of Al ２ O ３ In Non-Patent Document 1, the wavelength of the laser light is 4.6 μm, and at this wavelength, SiO ２ It can be said that this is preferable. However, when targeting a wavelength of 9 μm as in this embodiment, SiO ２ Al absorbs less light than Al. ２ O ３ This is preferable.

[0043] Figure 5 shows the result of calculating the reflectance of the reflective film 11 according to the comparative example as a function of the film thickness d3 of the third layer film 15. In the calculation, based on Non-Patent Literature 2, Al ２ O ３ n1 is the complex refractive index at a wavelength of 9 μm. ＊ = 1.13309 + i0.08571. Also, based on Non-Patent Document 3, the complex refractive index of Ti at a wavelength of 9 μm is given by n2 ＊ = 6.46976 + i16.50695. Furthermore, based on Non-Patent Document 3, the complex refractive index of Au at a wavelength of 9 μm is given by n3 ＊ = 9.42171 + i55.49599.

[0044] As shown in Figure 5, the reflectance of the comparative example saturates in the region where the film thickness d3 is 50 nm or more, but the maximum is only about 95.5%. Although the reflectance of the comparative example is higher than the reflectance R0 when there is no reflective film 11, it is still lower than the reflectance of the reflective film 11 of this disclosure.

[0045] <Method for Manufacturing a Semiconductor Laser Device> Figure 6 is a diagram showing a method for manufacturing an optical device 100 according to Embodiment 1. The reflective film 11 of the optical device 100 of this disclosure can be formed using a reactive sputtering apparatus 200.

[0046] Here, as an example, we will describe the case where the reactive sputtering apparatus 200 is an electron cyclotron resonance (ECR) plasma deposition apparatus. However, the plasma generation method is not limited.

[0047] In the plasma generation chamber 21, a plasma flow 26 is generated by microwave electron cyclotron resonance discharge against the gas introduced from the first gas introduction system 32. The generated plasma flow 26 is introduced into the sample chamber 22 through the plasma extraction window 25. In the sample chamber 22, the sputtering target 36 is positioned near the plasma extraction window 25. The sputtering target 36 is sputtered by the plasma flow 26 introduced into the sample chamber 22, generating ions.

[0048] The material of the sputtering target 36 is a metal commonly used for the first layer 13, the second layer 14, and the third layer 15. In this embodiment, Ta is used as the sputtering target 36.

[0049] In the sample chamber 22, the sample 27 is placed on the sample stage 28. A plasma stream 26, which incorporates ions generated from the target 36, is incident on the sample 27, causing a thin film containing the material of the target 36 to form on the surface of the sample 27.

[0050] The reactive sputtering apparatus 200 has two gas introduction systems: a first gas introduction system 32 and a second gas introduction system 33. The first gas introduction system 32 is used to supply a gas for plasma generation to the plasma generation chamber 21. Ar, an inert gas, is particularly preferred as the gas for plasma generation, but other gases may also be used. The second gas introduction system 33 is used to supply a raw material gas for the reflective film 11 to the sample chamber 22. The raw material gas is O, which is used to generate metal oxides for the first layer film 13 and the third layer film 15. ２ That is the case.

[0051] Figure 7 is a top view of a sample 27 according to Embodiment 1, and Figure 8 is a cross-sectional view taken along the xa-xb line in Figure 7. Multiple bar-shaped semiconductor stacks 12, with their rear end faces facing upward (z direction), are placed on the base of a vise-shaped fixing device 44. Dummy bars 42 made of Si or stainless steel (SUS) are placed between each semiconductor stack 12 to prevent contact between the semiconductor stacks 12. The alternately arranged semiconductor stacks 12 and dummy bars 42 are sandwiched from both sides by retaining plates 43. The semiconductor stacks 12 and dummy bars 42 are fastened together by screws 45 of the fixing device 44 via the retaining plates 43.

[0052] In preparing sample 27, first a retaining plate 43 is placed at one end of the base of the fixing device 44, and dummy bars 42 and semiconductor laminates 12 with their rear end faces facing upwards are alternately placed next to the retaining plate 43. Furthermore, retaining plates 43 are placed at the ends of the alternately arranged semiconductor laminates 12 and dummy bars 42. Finally, sample 27 is completed by tightening the semiconductor laminates 12 and dummy bars 42 with screws 45 of the fixing device 44 via the retaining plates 43.

[0053] In the fabrication of the optical device 100 using the reactive sputtering apparatus 200, first, the sample 27 is placed on the sample stage 28. Next, Ar is supplied from the first gas introduction system 32, and O is supplied from the second gas introduction system 33. ２ The first layer film 13 of Ta is supplied. In this state, the sputtering target 36, Ta, is sputtered and the first layer film 13 of Ta is applied to the rear end surface of the semiconductor laminate 12. ２ O ５ A thin film is formed.

[0054] Furthermore, while the supply of Ar from the first gas introduction system 32 continues, the second gas introduction system 33 is O ２ The supply of is stopped. In this state, the sputtering target 36, which is Ta, is sputtered to deposit the second layer 14, which is Ta, on the first layer 13.

[0055] Furthermore, O from the second gas introduction system 33 ２ The supply will be resumed. In this state, the sputtering target 36, which is Ta, will be sputtered, and the third layer 15, which is Ta, will be placed on the second layer 14. ２ O ５ A film is formed. This makes it possible to manufacture an optical device 100 in which a reflective film 11 is provided on the rear end surface of the semiconductor laminate 12.

[0056] As described above, in this embodiment, the optical device 100 has a first layer film 13, a second layer film 14, and a third layer film 15, which is the outermost layer, stacked in this order on the rear end surface of the semiconductor laminate 12. The first layer film 13 and the third layer film 15 are metal oxides, and the second layer film 14 is an element of the metal contained in the metal oxides of the first layer film 13 and the third layer film 15.

[0057] Furthermore, in the manufacture of the optical device 100 of this embodiment, the metal used in common for the first layer film 13, the second layer film 14, and the third layer film 15 is used as the material for the sputtering target 36. Also, to generate the oxide of the said metal, ２The raw material gas is used. The first layer film 13 and the third layer film 15, which are metal oxides, can be formed in a reactive sputtering apparatus 200 by supplying the raw material gas to the sample chamber 22 and then sputtering the sputtering target 36. The second layer film 14 can be formed by stopping the supply of the raw material gas and then sputtering the sputtering target 36. This makes it possible to provide an optical device 100 having a reflective film 11 that can be formed with a single film deposition apparatus, and a method for manufacturing the same.

[0058] <Modification> Note that the end face on which the reflective film 11 is provided is not necessarily limited to the rear end face, but may also be provided on the laser beam emission surface. In other words, it is sufficient that the reflective film 11 is provided on at least one of the end faces of the semiconductor laminate 12 that face the direction of the laser beam guidance. This is common to all embodiments.

[0059] Embodiment 2 In this embodiment, we will describe the case where the metal is Al in a reflective film 11 in which the first layer film 13 and the third layer film 15 are metal oxides and the second layer film 14 is the elemental metal. The following will describe the changes from Embodiment 1.

[0060] In this embodiment, the first layer 13 is made of Al with a thickness of 300 nm. ２ O ３ The second layer 14 is Al, and the third layer 15 is Al with a thickness of 100 nm. ２ O ３ That is the case.

[0061] Figure 9 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 2 as a function of the film thickness d2 of the second layer film 14. In the calculation, the wavelength of the laser light was set to 9 μm, as in Embodiment 1. Also, based on Non-Patent Literature 2, Al ２ O ３ n1 is the complex refractive index at a wavelength of 9 μm. ＊ = n3 ＊ = 1.13309 + i0.08571. Also, based on Non-Patent Document 3, the complex refractive index of Al at a wavelength of 9 μm is given by n2 ＊ = 19.66369 + i77.26043.

[0062] As shown in the figure, the reflectivity shows a tendency to saturate in the region where the film thickness d2 is 40 nm or more, reaching 96% or more. In other words, a high reflectivity similar to that of Embodiment 1 can be obtained in this embodiment as well. Furthermore, as shown in the figure, it can be said that a film thickness d2 of 40 nm or more for the second layer film 14 in this embodiment is particularly preferable.

[0063] Furthermore, the third layer 15 of this embodiment is Al ２ O ３ Therefore, it is a material that does not contain Au. For this reason, when the solder used to join the optical device 100 to the submount is AuSn solder, it is possible to prevent the solder from creeping up.

[0064] <Method for Manufacturing Semiconductor Laser Device> In the manufacturing of the optical device 100 of this embodiment, Al, which is used in common for the first layer film 13, the second layer film 14, and the third layer film 15, is used as the material for the sputtering target 36. In addition, O is used to generate Al oxide. ２ This will be used as the raw material gas.

[0065] In the fabrication of the optical device 100, first, a sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and O is supplied from the second gas introduction system 33. ２ This is supplied. By sputtering the Al sputtering target 36 in this state, the first layer film 13, which is Al, is formed on the rear end surface of the semiconductor laminate 12. ２ O ３ A film is formed. Furthermore, O from the second gas introduction system 33 ２ After stopping the supply of oxygen, the sputtering target 36 is sputtered to deposit the second layer film 14, which is Al, on the first layer film 13. Furthermore, oxygen from the second gas introduction system 33 is introduced. ２ The supply of is resumed, and by sputtering the sputtering target 36, the third layer 15 Al is formed on the second layer 14. ２ O ３ This allows for the formation of a film. This makes it possible to provide an optical device 100 having a reflective film 11 that can be formed using a single film deposition apparatus, and a method for manufacturing the same.

[0066] Embodiment 3 In this embodiment, we will describe a reflective film 11 in which the first layer 13 and the third layer 15 are metal oxides and the second layer 14 is the elemental metal, and in which case the metal is Ti. The following will describe the changes from Embodiment 1.

[0067] In this embodiment, the first layer 13 is a TiO2 film with a thickness of 500 nm. ２ The second layer 14 is Ti, and the third layer 15 is TiO with a thickness of 100 nm. ２ That is the case.

[0068] Figure 10 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 3 as a function of the film thickness d2 of the second layer film 14. In the calculation, the wavelength of the laser light was set to 9 μm, as in Embodiment 1. Also, based on Non-Patent Literature 2, TiO ２ n1 is the complex refractive index at a wavelength of 9 μm. ＊ = n3 ＊ = 1.64865 + i0.06818. Also, based on Non-Patent Document 3, the complex refractive index of Ti at a wavelength of 9 μm is given by n2 ＊ = 6.46976 + i16.50695.

[0069] As shown in the figure, the reflectivity tends to saturate in the region where the film thickness d2 is 110 nm or more, reaching 80% or more. In other words, a high reflectivity can be obtained in this embodiment as well. Furthermore, as shown in the figure, it can be said that a film thickness d2 of 110 nm or more for the second layer film 14 in this embodiment is particularly preferable.

[0070] Furthermore, the third layer 15 of this embodiment is TiO ２ Therefore, it is a material that does not contain Au. For this reason, when the solder used to join the optical device 100 to the submount is AuSn solder, it is possible to prevent the solder from creeping up.

[0071] <Method for Manufacturing Semiconductor Laser Device> In the manufacturing of the optical device 100 of this embodiment, Ti, which is used in common for the first layer film 13, the second layer film 14, and the third layer film 15, is used as the material for the sputtering target 36. Also, O is used to generate the oxide of Ti. ２ This will be used as the raw material gas.

[0072] In the fabrication of the optical device 100, first, a sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and O is supplied from the second gas introduction system 33. ２ This is supplied. By sputtering the Ti sputtering target 36 in this state, the first layer film 13, which is TiO, is formed on the rear end surface of the semiconductor laminate 12. ２ A film is formed. Furthermore, O from the second gas introduction system 33 ２ After stopping the supply of the oxygen, the sputtering target 36 is sputtered to deposit a Ti second layer 14 on the first layer 13. Furthermore, oxygen from the second gas introduction system 33 is introduced. ２ The supply of TiO is resumed, and the sputtering target 36 is sputtered to form a third layer 15 on top of the second layer 14. ２ This allows for the formation of a film. This makes it possible to provide an optical device 100 having a reflective film 11 that can be formed using a single film deposition apparatus, and a method for manufacturing the same.

[0073] Embodiment 4 In Embodiments 1 to 3, the first layer film 13 and the third layer film 15 were described as metal oxides. However, the first layer film 13 and the third layer film 15 may also be metal nitrides.

[0074] In this embodiment, the first layer 13 is AlN with a thickness of 450 nm, the second layer 14 is Al, and the third layer 15 is AlN with a thickness of 100 nm.

[0075] Figure 11 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 4 as a function of the film thickness d2 of the second layer film 14. In the calculation, the wavelength of the laser light was set to 9 μm, as in Embodiment 1. Also, based on Non-Patent Literature 2, the complex refractive index of AlN at a wavelength of 9 μm was set to n1 ＊ = n3 ＊ = 1.19630 + i0.04745. Also, based on Non-Patent Document 3, the complex refractive index of Al at a wavelength of 9 μm is given by n2 ＊ = 19.66369 + i77.26043.

[0076] As shown in the figure, in the region where the film thickness d2 is 30 nm or more, the reflectivity reaches approximately 96%, and a high reflectivity similar to that of Embodiment 1 is obtained. Furthermore, as shown in the figure, it can be said that a film thickness d2 of 30 nm or more for the second layer film 14 in this embodiment is particularly preferable.

[0077] Furthermore, the third layer 15 in this embodiment is AlN and is a material that does not contain Au. Therefore, when the solder used to join the optical device 100 to the submount is AuSn solder, it is possible to prevent the solder from creeping up.

[0078] <Method for Manufacturing Semiconductor Laser Device> In the manufacturing of the optical device 100 of this embodiment, Al, which is commonly used in the first layer film 13, the second layer film 14, and the third layer film 15, is used as the material for the sputtering target 36. In addition, N is used to generate Al nitrides. ２ This will be used as the raw material gas.

[0079] In the fabrication of the optical device 100, first, a sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and N is supplied from the second gas introduction system 33. ２ N is supplied. In this state, the Al sputtering target 36 is sputtered to form the first layer film 13, which is AlN, on the rear end surface of the semiconductor laminate 12. Furthermore, N from the second gas introduction system 33 ２ After stopping the supply of N, the sputtering target 36 is sputtered to deposit the second layer film 14, which is Al, on the first layer film 13. Furthermore, N from the second gas introduction system 33 ２ The supply of the material is resumed, and the AlN third layer 15 is deposited on the second layer 14 by sputtering the sputtering target 36. This makes it possible to provide an optical device 100 having a reflective film 11 that can be deposited with a single deposition apparatus, and a method for manufacturing the same.

[0080] <Modification> The combination of metal nitride and metal may be TaN and Ta. In this case as well, the same effects as those described in Embodiment 4 can be obtained.

[0081] Embodiment 5 The first layer film 13 and the third layer film 15 do not necessarily have to be made of the same material. The first layer film 13 may be made of a metal oxide, and the third layer film 15 may be made of a metal nitride.

[0082] In this embodiment, the first layer film 13 is Al with a film thickness of 450 nm ２ O ３ , the second layer film 14 is Al, and the third layer film 15 is AlN with a film thickness of 100 nm.

[0083] FIG. 12 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 5 as a function of the film thickness d2 of the second layer film 14. In the calculation, the wavelength of the laser light was set to 9 μm as in Embodiment 1. Also, based on Non-Patent Document 2, the complex refractive index of Al ２ O ３ at a wavelength of 9 μm was set to n1 ＊ = 1.13309 + i0.08571. Also, based on Non-Patent Document 2, the complex refractive index of AlN at a wavelength of 9 μm was set to n3 ＊ = 1.19630 + i0.04745. Also, based on Non-Patent Document 3, the complex refractive index of Al at a wavelength of 9 μm was set to n2 ＊ = 19.66369 + i77.26043.

[0084] From the figure, in the region where the film thickness d2 is 40 nm or more, the reflectance reaches about 96%, and a high reflectance comparable to that of Embodiment 1 can be obtained. Also, from the figure, it can be said that a film thickness d2 of 40 nm or more for the second layer film 14 in this embodiment is particularly suitable.

[0085] <Method for manufacturing a semiconductor laser device> In the manufacture of the optical device 100 of this embodiment, Al commonly used for the first layer film 13, the second layer film 14, and the third layer film 15 is used as the material of the sputtering target 36. Also, as the raw material gas, O ２ for generating an oxide of Al and N ２ for generating a nitride are used.

[0086] In the production of the optical device 100, first, the sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and O ２This is supplied. By sputtering the Al sputtering target 36 in this state, the first layer film 13, which is Al, is formed on the rear end surface of the semiconductor laminate 12. ２ O ３ A film is formed. Furthermore, O from the second gas introduction system 33 ２ After stopping the supply of the fuel, the sputtering target 36 is sputtered to deposit the second layer film 14, which is Al, on the first layer film 13. Furthermore, the raw material gas supplied to the second gas introduction system 33 is changed to O ２ From N ２ The process is switched to sputtering the sputtering target 36 to deposit the AlN third layer 15 on the second layer 14. This makes it possible to provide an optical device 100 having a reflective film 11 that can be deposited using a single deposition apparatus, and a method for manufacturing the same.

[0087] Embodiment 6 Conversely to Embodiment 5, the first layer film 13 may be a metal nitride and the third layer film 15 may be a metal oxide.

[0088] In this embodiment, the first layer 13 is AlN with a thickness of 450 nm, the second layer 14 is Al, and the third layer 15 is Al with a thickness of 100 nm. ２ O ３ That is the case.

[0089] Figure 13 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 6 as a function of the film thickness d2 of the second layer film 14. In the calculation, the wavelength of the laser light was set to 9 μm, as in Embodiment 1. Also, based on Non-Patent Literature 2, the complex refractive index of AlN at a wavelength of 9 μm was set to n1 ＊ = 1.19630 + i0.04745. Also, based on Non-Patent Document 2, Al ２ O ３ n3 is the complex refractive index at a wavelength of 9 μm. ＊ = 1.13309 + i0.08571. Also, based on Non-Patent Document 3, the complex refractive index of Al at a wavelength of 9 μm is given by n2 ＊ = 19.66369 + i77.26043.

[0090] As shown in the figure, in the region where the film thickness d2 is 40 nm or more, the reflectivity reaches approximately 96%, and a high reflectivity similar to that of Embodiment 1 is obtained. Furthermore, as shown in the figure, it can be said that a film thickness d2 of 40 nm or more for the second layer film 14 in this embodiment is particularly preferable.

[0091] Furthermore, since the first layer film 13 in this embodiment is AlN, which has high thermal conductivity, it is possible to suppress the temperature rise near the rear end surface of the semiconductor laminate 12.

[0092] <Method for Manufacturing Semiconductor Laser Device> In the manufacturing of the optical device 100 of this embodiment, Al, which is commonly used in the first layer film 13, the second layer film 14, and the third layer film 15, is used as the material for the sputtering target 36. In addition, as the raw material gas, O is used to generate Al oxide. ２ And, N for producing nitrides ２ Two types are used.

[0093] In the fabrication of the optical device 100, first, a sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and N is supplied from the second gas introduction system 33. ２ N is supplied. In this state, the Al sputtering target 36 is sputtered to form the first layer film 13, which is AlN, on the rear end surface of the semiconductor laminate 12. Furthermore, N from the second gas introduction system 33 ２ After stopping the supply of the fuel, the sputtering target 36 is sputtered to deposit the second layer film 14, which is Al, on the first layer film 13. Furthermore, the raw material gas supplied to the second gas introduction system 33 is changed to N ２ From O ２ Switching to this setting, the sputtering target 36 is sputtered, thereby forming the third layer 15, which is Al, on top of the second layer 14. ２ O ３ This allows for the formation of a film. This makes it possible to provide an optical device 100 having a reflective film 11 that can be formed using a single film deposition apparatus, and a method for manufacturing the same.

[0094] Embodiment 7 The first layer film 13 may be a plurality of layers including a layer of metal oxide and a layer of the nitride of the metal.

[0095] Figure 14 is an enlarged cross-sectional view of the reflective film 11 according to Embodiment 7. The first layer film 13 of this embodiment includes a first layer film 13-1 provided on the rear end surface of the semiconductor laminate 12 and a first layer film 13-2 provided between the first layer film 13-1 and the second layer film 14. In this embodiment, the first layer film 13-1 on the rear end surface side is made of Al with a film thickness of 100 nm. ２ O ３ The first layer 13-2 is AlN with a thickness of 300 nm, the second layer 14 is Al, and the third layer 15 is AlN with a thickness of 100 nm.

[0096] Hereafter, the complex refractive index of the first layer film 13-1 is set to n11 ＊ The film thickness is set to d11. The complex refractive index of the first layer film 13-2 is set to n12. ＊ The film thickness is set to d12.

[0097] Figure 15 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 7 as a function of the film thickness d2 of the second layer film 14.

[0098] In the calculation, the wavelength of the laser light was set to 9 μm, as in Embodiment 1. Also, based on Non-Patent Document 2, Al ２ O ３ n11 is the complex refractive index at a wavelength of 9 μm. ＊ = 1.13309 + i0.08571. Also, based on Non-Patent Document 2, the complex refractive index of AlN at a wavelength of 9 μm is n12 ＊ = n3 ＊ = 1.19630 + i0.04745. Also, based on Non-Patent Document 3, the complex refractive index of Al at a wavelength of 9 μm is given by n2 ＊ = 19.66369 + i77.26043.

[0099] As shown in the figure, in the region where the film thickness d2 is 30 nm or more, the reflectivity reaches approximately 96%, and a high reflectivity similar to that of Embodiment 1 is obtained. Furthermore, as shown in the figure, it can be said that a film thickness d2 of 30 nm or more for the second layer film 14 in this embodiment is particularly preferable.

[0100] <Method for Manufacturing Semiconductor Laser Device> In the manufacturing of the optical device 100 of this embodiment, Al, which is commonly used in the first layer film 13, the second layer film 14, and the third layer film 15, is used as the material for the sputtering target 36. In addition, as the raw material gas, O is used to generate Al oxide. ２ And, N for producing nitrides ２ Two types are used.

[0101] In the fabrication of the optical device 100, first, a sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and O is supplied from the second gas introduction system 33. ２ This is supplied. In this state, by sputtering the Al sputtering target 36, the first layer film 13-1, Al, is formed on the rear end surface of the semiconductor laminate 12. ２ O ３ A thin film is formed.

[0102] Furthermore, the raw material gas supplied to the second gas introduction system 33 is O ２ From N ２ Switching to this setting, the sputtering target 36 is sputtered to deposit AlN, which is the first layer film 13-2, on the first layer film 13-1.

[0103] Furthermore, N from the second gas introduction system 33 ２ After stopping the supply of N, the sputtering target 36 is sputtered to deposit the second layer film 14, which is Al, on the first layer film 13-2. Furthermore, N from the second gas introduction system 33 ２ The supply of the material is resumed, and the AlN third layer 15 is deposited on the second layer 14 by sputtering the sputtering target 36. This makes it possible to provide an optical device 100 having a reflective film 11 that can be deposited with a single deposition apparatus, and a method for manufacturing the same.

[0104] Embodiment 8 The third layer 15 is not necessarily provided. That is, the reflective film 11 may have a two-layer structure consisting of a first layer 13 and a second layer 14.

[0105] Figure 16 is an enlarged cross-sectional view of the reflective film 11 according to Embodiment 8. The reflective film 11 of this embodiment has a two-layer structure consisting of a first layer film 13 and a second layer film 14. The first layer film 13 has a thickness of 100 nm or 300 nm of Ta ２ O ５ The second layer 14 is made of Ta.

[0106] Figure 17 shows the result of calculating the reflectance of the reflective film 11 according to Embodiment 8 as a function of the film thickness d2 of the second layer film 14. In the figure, the dashed line represents the reflectance when the film thickness d1 of the first layer film 13 is 100 nm, and the solid line represents the reflectance when the film thickness is 300 nm.

[0107] In the calculation, as an example, the reflectance at a wavelength of 9 μm was calculated. Also, based on Non-Patent Document 4, Ta ２ O ５ n1 is the complex refractive index at a wavelength of 9 μm. ＊ = 1.50333 + i0.00000, where i is the imaginary unit. Also, based on Non-Patent Document 5, the complex refractive index of Ta at a wavelength of 9 μm is given by n² ＊ = 10.68374 + i48.47897.

[0108] As shown in the figure, when the film thickness d1 of the first layer 13 is 100 nm, the reflectance of the second layer 14 reaches approximately 94% in the region where the film thickness d2 is 60 nm or more, and a high reflectance similar to that of Embodiment 1 is obtained. Also, when the film thickness d1 of the first layer 13 is 300 nm, the reflectance of the second layer 14 reaches approximately 94% in the region where the film thickness d2 is 40 nm or more, and a high reflectance similar to that of Embodiment 1 is obtained. Therefore, it can be said that a film thickness d2 of the second layer 14 of 40 nm or more is particularly preferable in this embodiment.

[0109] <Method for Manufacturing Semiconductor Laser Device> In the manufacturing of the optical device 100 of this embodiment, Ta, which is used in common for the first layer film 13 and the second layer film 14, is used as the material for the sputtering target 36. Also, O is used to generate the oxide of Ta. ２ This will be used as the raw material gas.

[0110] In the fabrication of the optical device 100, first, a sample 27 of the semiconductor laminate 12 is placed on the sample stage 28 of the reactive sputtering apparatus 200. Next, Ar is supplied from the first gas introduction system 32, and O is supplied from the second gas introduction system 33. ２ This is supplied. In this state, by sputtering the Ta sputtering target 36, the first layer film 13 of Ta is formed on the rear end surface of the semiconductor laminate 12. ２ O ５ A film is formed. Furthermore, O from the second gas introduction system 33 ２ After stopping the supply of the material, the sputtering target 36 is sputtered to deposit a second layer film 14, which is Ta, on the first layer film 13.

[0111] As described above, in the manufacture of the optical device 100 of this embodiment, the material of the sputtering target 36 is a metal that is commonly used for the first layer film 13 and the second layer film 14. Furthermore, if the first layer film 13 is a metal oxide, oxygen is used as the raw material gas, and if the first layer film is a metal nitride, nitrogen is used as the raw material gas. The first layer film 13, which is a metal oxide, can be formed in a reactive sputtering apparatus 200 by supplying the raw material gas to the sample chamber 22 and then sputtering the sputtering target 36. The second layer film 14 can be formed by stopping the supply of the raw material gas and then sputtering the sputtering target 36. This makes it possible to provide an optical device 100 having a reflective film 11 that can be formed with a single film deposition apparatus, and a method for manufacturing the same.

[0112] Furthermore, the second layer 14 in this embodiment is Ta, which is a metal other than Au. Therefore, it can prevent the AuSn solder from creeping up and can perform the same role as the third layer 15.

[0113] This disclosure is not limited to the embodiments described above, and various modifications can be made during implementation without departing from its essence. Furthermore, each embodiment and its modifications may be combined as appropriate, and in that case, the combined effects can be obtained.

[0114] The metals used in this disclosure are not limited to Ta, Al, and Ti, but may also be other metals such as W (tungsten), Mo (molybdenum), and Ce (cerium). Specifically, the combination of metal oxides and metals is WO ２ or WO ３ And W, MoO ３ And Mo, CEO ２ By using Ce, the same effects as those described in each embodiment can be obtained.

[0115] The optical device 100 is not limited to a semiconductor laser device provided with a reflective film 11, but may also be a photodiode (PD) or an electroabsorption (EA) modulator provided with a reflective film 11. In this case, the semiconductor laminate 12 only needs to include at least an optical waveguide layer.

[0116] Furthermore, the optical device 100 of this disclosure may be an optical crystal such as lithium niobate (LiNbO3:LN) provided with a reflective film 11, a lens, or a prism.

[0117] In the claims, semiconductor laser devices, field absorption modulators, optical crystals, lenses, or prisms are collectively referred to as optical elements.

[0118] 1: First electrode, 2: Substrate, 3: Buffer layer, 4: Photoconfinement layer, 5: Core region, 6: Photoconfinement layer, 7: Cladding layer, 8: Contact layer, 9: Second electrode, 10: Current blocking layer, 11: Reflective film, 12: Semiconductor laminate, 13: First layer film, 13-1: First layer film, 13-2: First layer film, 14: Second layer film, 15: Third layer film, 21: Plasma generation chamber, 22: Sample chamber, 25: Plasma extraction window, 26: Plasma flow, 27: Sample, 28: Sample stage, 32: First gas introduction system, 33: Second gas introduction system, 36: Sputtering target, 42: Dummy bar, 43: Retaining plate, 44: Fixing device, 45: Screw, 100: Optical device, 200: Reactive sputtering apparatus

Claims

1. An optical device comprising an optical element and a reflective film provided on an end face of the optical element facing the direction of light guidance, wherein the reflective film has a first layer film provided on the end face of the optical element that transmits light and a second layer film provided on the first layer film that reflects light, the first layer film being a metal oxide or nitride and the second layer film being the metal.

2. The optical device according to claim 1, wherein the optical element is a semiconductor laminate including a light waveguide layer.

3. The optical device according to claim 1 or 2, further comprising a third layer film provided on the second layer film, wherein the third layer film is an oxide or nitride of the metal.

4. The optical device according to any one of claims 1 to 3, wherein the first layer film comprises a plurality of layers including a layer of metal oxide and a layer of metal nitride.

5. The optical device according to any one of claims 1 to 4, wherein the metal is one of Ta (tantalum), Al (aluminum), Ti (titanium), W (tungsten), Mo (molybdenum), and Ce (cerium).

6. The optical device according to claim 1 or 2, further comprising a third layer provided on the second layer, wherein the material of the third layer is a metal-free material used for soldering the optical device to a submount.

7. A method for manufacturing an optical device according to any one of claims 1 to 6, wherein oxygen is used as a raw material gas when the first layer film is an oxide of the metal, and nitrogen is used when the first layer film is a nitride of the metal; the optical element is placed in the sample chamber of a reactive sputtering apparatus; the first layer film is formed on the end face of the optical element by sputtering a sputtering target made of the metal while the raw material gas is supplied to the sample chamber; and the second layer film is formed on the first layer film by sputtering the sputtering target after stopping the supply of the raw material gas.

8. A method for manufacturing an optical device according to claim 3 or 6, wherein the first layer film is an oxide of the metal, oxygen is used as the first raw material gas if the first layer film is an oxide of the metal, and nitrogen is used as the first raw material gas if the first layer film is an oxide of the metal; the optical element is placed in the sample chamber of a reactive sputtering apparatus; the first layer film is formed on the end face of the optical element by sputtering a sputtering target made of the metal while the first raw material gas is supplied to the sample chamber; the second layer film is formed on the first layer film by sputtering the sputtering target after stopping the supply of the first raw material gas; the third layer film is formed on the second layer film by sputtering the sputtering target while the second raw material gas is supplied, and oxygen is used as the second raw material gas if the third layer film is an oxide of the metal, and nitrogen is used as the second raw material gas if the third layer film is an oxide of the metal; the third layer film is formed on the second layer film by sputtering the sputtering target while the second raw material gas is supplied.

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