Semiconductor optical integrated element

Abstract

This semiconductor optical integrated element is provided with: an InxGa1-xAsyP1-y (0 < = x < = 1, 0 < = y < = 1) layer formed on the outermost surface of a semiconductor laminate having a high mesa ridge structure; a first nitride film formed on the InxGa1-xAsyP1-y (0 < = x < = 1, 0 < = y < = 1) layer by a CVD method or an ALD method; an insulating intermediate film formed on the first nitride film from a polymer compound layer or an insulating film formed by a CVD method, the insulating intermediate film having a film thickness of # imgabs0 # or more; and a second nitride film formed on the insulating intermediate film using a CVD method and having a film thickness of # imgabs1 # or more or a nitride film formed using an ALD method and having a film thickness of # imgabs2 # or more. As a result, it is possible to provide a semiconductor optical integrated element having a high mesa ridge structure, the semiconductor optical integrated element having a surface protection film which has covering properties and in which peeling and floating are suppressed.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor optical integrated device having a high mesa ridge structure and provided with an insulating film on the surface of a semiconductor layer. Background Art

[0002] In the access network of the optical communication system between the relay station and the user, an electro-absorption modulator integrated laser (EML) is used as a semiconductor optical integrated component that integrates a semiconductor laser that outputs a single wavelength of light, such as an electro-absorption modulator (EAM) suitable for high-speed modulation and a distributed feedback laser diode (DFB-LD or DFB laser).

[0003] Since semiconductor optical integrated elements can be used in high temperature and high humidity environments, a surface protection film is usually provided on the surface of the semiconductor layer mainly to ensure moisture resistance. When forming the surface protection film, the surface protection film is thickened to ensure coverage. In addition, the thickening of the surface protection film also has the effect of reducing the insulating film capacitance of the insulating film constituting the surface protection film. In particular, in semiconductor optical integrated elements having a high terrace ridge structure with an uneven surface of more than 3μm, since the side wall of the high terrace ridge structure is difficult to be covered, there is a situation where the film needs to be thickened to ensure coverage. On the other hand, since the thickening of the surface protection film is accompanied by an increase in film stress, there is a situation where the surface protection film peels off and floats. In addition, since there is a situation where the film quality changes during the heat treatment of the manufacturing process after the surface protection film is formed, there is a concern about the peeling and floating of the surface protection film.

[0004] Japanese Patent Application Publication No. 61-112386 discloses a technique for thickening a surface protective film by using a three-layer insulating film, but does not consider application to semiconductor optical integrated devices having a high terrace ridge structure, and cannot fully solve concerns about peeling and floating of the surface protective film.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 61-112386

[0006] In the case of semiconductor optical integrated components having a high terrace ridge structure, it is difficult to form a surface protective film on the sidewall of the high terrace ridge structure compared to the surface of the semiconductor layer, and in order to ensure coverage, the surface protective film needs to be further thickened. On the other hand, since the stress of the surface protective film increases with the further thickening of the surface protective film, the concern about peeling and floating of the surface protective film is further increased. Therefore, when forming a surface protective film for a semiconductor optical integrated component having a high terrace ridge structure, there is the following issue: a trade-off needs to be made between ensuring coverage and the concern about peeling and floating of the surface protective film. Summary of the invention

[0007] The present disclosure has been made to solve the above-mentioned problems and aims to obtain a semiconductor optical integrated device in which a surface protection film having coverage even for a high mesa ridge structure is formed and at the same time, peeling and lifting of the surface protection film from a semiconductor layer are suppressed.

[0008] A semiconductor optical integrated component, comprising: x Ga 1－x As y P 1－y (0≤x≤1, 0≤y≤1) layer, formed on the outermost surface of the semiconductor stack having a high terrace ridge structure; a first nitride film, formed on the In layer by CVD or ALD x Ga 1－ x As y P 1－y (0≤x≤1, 0≤y≤1) layer; an insulating intermediate film, which is composed of a polymer compound layer or an insulating film formed by a CVD method on the first nitride film, and has and a second nitride film having a thickness of The thickness of the above nitride film or the film formed by the ALD method is The above nitride film.

[0009] According to the present disclosure, a surface protection film including a first nitride film for ensuring coverage and adhesion, an insulating intermediate film for thickening the coverage and surface protection film, and a second nitride film for moisture resistance can be formed. Therefore, a semiconductor optical integrated element having a high terrace ridge structure and a surface protection film that has coverage and suppresses peeling and floating can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the appearance of EML1 involved in Embodiment 1.

[0011] Figure 2AA is a schematic cross-sectional view of the DFB-LD portion 10 of the EML 1 according to the first embodiment.

[0012] Figure 3 BB is a schematic cross-sectional view of the EAM portion 20 of the EML 1 according to the first embodiment.

[0013] Figure 4 AA is a schematic cross-sectional view of the DFB-LD portion 10 of the EML 1 showing the structure of the surface protection film according to the first embodiment.

[0014] Figure 5 BB is a schematic cross-sectional view of the EAM portion 20 of the EML 1 showing the structure of the surface protection film according to the first embodiment.

[0015] Figure 6 These are microscope photographs after heat treatment in a case where the surface protection film according to Embodiment 1 is applied and a case where the surface protection film is not applied.

[0016] Figure 7 AA is a schematic cross-sectional view of the DFB-LD portion 10 of the EML 1 showing the structure of the surface protection film according to the second embodiment.

[0017] Figure 8 BB is a schematic cross-sectional view of the EAM portion 20 of the EML 1 showing the structure of the surface protection film according to the second embodiment. DETAILED DESCRIPTION

[0018] An example of a semiconductor optical integrated device according to the present disclosure is shown below, but the present disclosure is not limited to the following embodiments and can be arbitrarily modified within the scope of the present disclosure. In addition, for the sake of convenience, the description of "CVD method" in this specification refers to "CVD method other than ALD method".

[0019] Implementation Method 1

[0020] Figure 1 It is a schematic diagram of the appearance of EML1 involved in Embodiment 1. Figure 2 AA is a schematic cross-sectional view of the DFB-LD portion 10 of the EML 1 according to the first embodiment. Figure 3 BB is a schematic cross-sectional view of the EAM portion 20 of the EML 1 according to the first embodiment. Figure 4 AA is a schematic cross-sectional view of the DFB-LD portion 10 of the EML 1 showing the structure of the surface protection film according to the first embodiment. Figure 5 BB is a schematic cross-sectional view of the EAM portion 20 of the EML 1 showing the structure of the surface protection film according to the first embodiment. Figure 6These are external appearance diagrams after heat treatment when the surface protection film according to Embodiment 1 is applied and when the surface protection film is not applied.

[0021] In Embodiment 1, EML 1 is exemplified as a semiconductor optical integrated device. Figure 1 As shown, the DFB-LD section 10 and the EAM section 20 are provided. The cross-sectional structure of the DFB-LD section 10 is as follows Figure 2 As shown in the figure, a barrier layer including a p-type InP layer 201, an n-type InP layer 202, and a p-type InP layer 203 is formed on an n-type InP substrate 101 in this order from the bottom. On the barrier layer, a p-type InP layer 301 and a p-type InGaAs layer 302 are formed in this order from the bottom as contact layers. In other words, a semiconductor stacked body including barrier layers and contact layers on an n-type InP substrate 101 is formed, and the p-type InGaAs layer 302 is the outermost layer of the contact layer. In Embodiment 1, the p-type InGaAs layer 302 is shown as the outermost layer of the contact layer, that is, the InGaAs layer 302 in the case of y=1. x Ga 1－x As y P 1－y (0≤x≤1, 0≤y≤1) layer, but is not limited thereto, and any In can be applied within the range of 0≤x≤1 and 0≤y≤1 x Ga 1－x As y P 1－y layer. In addition, the resonator 400 portion has a ridge structure that is etched deeper than the active layer 500, namely, a so-called high terrace ridge structure. A surface protection film 600 is formed on the p-type InGaAs layer 302 to cover the surface of the p-type InGaAs layer 302. A surface electrode 701 serving as an anode electrode is formed on the surface protection film 600, and a back electrode 702 serving as a cathode electrode is formed on the lower surface of the n-type InP substrate 101. In addition, as Figure 3 As shown in FIG. 1 , the cross-sectional structure of the EAM portion 20 is also the same as that of the DFB-LD portion 10 , and thus a detailed description thereof will be omitted.

[0022] Next, use Figure 4 The cross-sectional schematic diagram of the DFB-LD section 10 shows the specific layer structure of the surface protection film 600. Figure 4 As shown, the surface protection film 600 is formed of a three-layer structure of a first nitride film 601, an insulating intermediate film 602, and a second nitride film 603 in order from the bottom.

[0023] First, the first nitride film 601 according to the first embodiment is a SiN film formed by PE-CVD (Plasma-Enhanced Chemical Vapor Deposition) method, and the film thickness is By applying a SiN film formed by the PE-CVD method, it is possible to have close adhesion with the semiconductor layer and cover the unevenness associated with the high terrace ridge structure. Therefore, even in the case of heat treatment after film formation, it is possible to suppress the peeling and floating of the insulating film from the semiconductor layer. In addition, the film seed of the first nitride film 601 is preferably a nitride film with good adhesion to the semiconductor layer. In addition to the SiN film, an AlN film can also be used. In addition, as a film forming method, a film forming method that can perform isotropic film formation is preferred so as to cover the unevenness associated with the high terrace ridge structure. It is not limited to the PE-CVD method, and CVD (Chemical Vapor Deposition) method and ALD (Atomic Layer Deposition) method can also be used. In addition, the film thickness is preferably 200 Å. The thickness above is formed so as to be able to cover the unevenness accompanying the high mesa ridge shape.

[0024] Next, the insulating intermediate film 602 is a SiO film formed by PE-CVD method, and the film thickness is By using the PE-CVD method, The thickness of SiO with a dielectric constant smaller than that of SiN is formed, so that the unevenness associated with the high terrace ridge structure can be further covered as in the first nitride film 601, while reducing the insulating film capacitance. In addition, although a SiO film is shown as a film type of the insulating intermediate film 602, it is more difficult to form a SiO film from the viewpoint of coverage and insulating film capacitance. The above film thickness is sufficient, and it is not limited to Si-based oxide films, and Si-based nitride films, Al-based oxide films, and Al-based nitride films can be arbitrarily applied. In addition, as a film forming method, a film forming method that can perform isotropic film formation in a manner that can cover the concave and convex accompanied by the high terrace ridge structure can be applied, and it is not limited to the PE-CVD method, and the CVD method can also be used.

[0025] Next, the second nitride film 603 is a SiN film formed by PE-CVD method, and has a refractive index in the range of 1.96 to 2.00. The film thickness is By forming the second nitride film 603 on the outermost side of the surface protection film 600, moisture resistance can be ensured. In addition, the film thickness of the second nitride film 603 can ensure moisture resistance, and is not limited to the PE-CVD method. In the case of a SiN film having a refractive index in the range of 1.96 or more and 2.00 or less, it can be formed by the CVD method. In addition, when the second nitride film 603 is formed by the ALD method, a more isotropic and dense insulating film can be formed compared with the CVD method, so the film type can be any Si-based or Al-based nitride film, and the film thickness is That’s all.

[0026] Figure 6 The following are photos of the appearance of the semiconductor optical integrated device according to the first embodiment and the semiconductor optical integrated device to which the comparative example technology is applied after heat treatment. As the comparative example, the first nitride film and the second nitride film are the same as those in the first embodiment, and the insulating intermediate film is different from that in the first embodiment, and a thickness of 10000 is formed by sputtering. Semiconductor optical integrated components made of SiO films. Figure 6 It can be seen that in the semiconductor optical integrated element involved in the first embodiment of the present disclosure, no peeling and floating of the surface protective film occurred, but in the semiconductor optical integrated element to which the technology of the comparative example was applied, multiple locations where peeling and floating of the surface protective film occurred occurred. In other words, it is shown that even if a heat treatment that is likely to cause peeling and floating of the surface protective film is applied after the surface protective film is formed, the effect of suppressing peeling and floating of the surface protective film can be obtained by applying the present disclosure.

[0027] In addition, although the mechanism of the effect of suppressing the peeling and floating of the surface protection film obtained by applying the present disclosure is not necessarily obvious, it can be inferred that one of the important factors is the three-layer structure including the first nitride film for ensuring coverage and adhesion, the insulating intermediate film for thickening the coverage and surface protection film, and the second nitride film for moisture resistance. This is because the difference in thermal expansion coefficients among the semiconductor, the first nitride film, the insulating intermediate film, and the second nitride film can be absorbed. In particular Figure 6 The results shown show that in addition to the first nitride film for ensuring coverage and adhesion to the semiconductor layer surface and the second nitride film responsible for moisture resistance, the insulating film having coverage is also applied to the insulating intermediate film formed between the first nitride film and the second nitride film, thereby achieving the effect of suppressing the peeling and floating of the surface protection film. This can be inferred that in addition to the difference in thermal expansion coefficients of the semiconductor, the first nitride film, the insulating intermediate film, and the second nitride film, the insulating intermediate film used in the technology as the comparative example is sputtered using a highly anisotropic sputtering method, so the thickness of the film formed along the semiconductor layer and the thickness of the film formed toward the side wall of the mesa ridge are relatively large, and as a result, the stress generated in the semiconductor and the surface protection film cannot be absorbed, causing the peeling and floating of the surface protection film.

[0028] By using the semiconductor optical integrated element configured in this way, an insulating film including a first nitride film for ensuring coverage and adhesion, a thickened insulating intermediate film for coverage and surface protection, and a second nitride film for moisture resistance can be formed.

[0029] Therefore, it is possible to provide a semiconductor optical integrated device having a high mesa ridge structure and including a surface protection film that has good coverage and suppresses peeling and floating.

[0030] Implementation Method 2

[0031] Figure 7 AA is a schematic cross-sectional view of the DFB-LD portion 10 of the EML 1 showing the structure of the surface protection film according to the second embodiment. Figure 8 BB is a schematic cross-sectional view of the EAM portion 20 of the EML 1 showing the structure of the surface protection film according to the second embodiment.

[0032] In implementation mode 2, Figure 7 as well as Figure 8 As shown, the surface protection film 600 is formed by applying an insulating intermediate film 604 with a thickness of The structure of the polyimide is composed of. The other structures except the insulating intermediate film 604 are the same as those in the first embodiment, so the detailed description is omitted. By using a film having a thickness of The polymer compound layer formed of polyimide can further cover the unevenness associated with the high terrace ridge structure and reduce the insulating film capacitance as in the first embodiment. In addition, although polyimide is shown as the film type of the insulating intermediate film 604, it is more convenient to form a high molecular compound layer from the viewpoint of coverage and insulating film capacitance. The above film thickness is sufficient and the film is not limited to polyimide, and any polymer compound used as an insulating base material can be applied.

[0033] By using the semiconductor optical integrated element configured in this way, an insulating film including a first nitride film for ensuring coverage and adhesion, a thickened insulating intermediate film for coverage and surface protection, and a second nitride film for moisture resistance can be formed.

[0034] Therefore, it is possible to provide a semiconductor optical integrated device having a high mesa ridge structure and including a surface protection film that has good coverage and suppresses peeling and floating.

[0035] Description of Reference Numerals

[0036] 1EML; 10DFB-LD portion; 20EAM portion; 101n-type InP substrate; 201p-type InP layer; 202n-type InP layer; 203p-type InP layer; 301p-type InP layer; 302p-type InGaAs layer; 400 resonator; 500 active layer; 600 surface protection film; 601 first nitride film; 602 insulating intermediate film; 603 second nitride film; 604 insulating intermediate film; 701 surface electrode; 702 back electrode.

Claims

1. A semiconductor optical integrated component, wherein: have: In x Ga 1－x As y P 1－y A layer is formed on the outermost surface of a semiconductor stack having a high terrace ridge structure, wherein 0≤x≤1, 0≤y≤1; The first nitride film is formed on the In by CVD or ALD method. x Ga 1－x As y P 1－y above the layer; The insulating intermediate film is composed of a polymer compound layer or an insulating film formed by a CVD method on the first nitride film, and has and The second nitride film is formed on the insulating intermediate film by CVD with a film thickness of The thickness of the above nitride film or the film formed by the ALD method is The above nitride film.

2. The semiconductor optical integrated device according to claim 1, wherein: The thickness of the first nitride film is above.

3. The semiconductor optical integrated device according to claim 1 or 2, wherein: The thickness of the insulating intermediate film is above.

4. The semiconductor optical integrated device according to any one of claims 1 to 3, wherein: The insulating intermediate film is a nitride film or an oxide film formed by a PE-CVD method.

5. The semiconductor optical integrated device according to any one of claims 1 to 4, wherein: The second nitride film has a refractive index of not less than 1.96 and not more than 2.00 and a film thickness of The above SiN film.

6. The semiconductor optical integrated device according to any one of claims 1 to 4, wherein: The second nitride film is a Si-based or Al-based nitride film formed by ALD method, and the film thickness is above.

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