Optical semiconductor device, optical transmission device provided with optical semiconductor device, and method for manufacturing optical transmission device

Abstract

This method for manufacturing an optical transmission device is provided with: a step for disposing an optical semiconductor device (1) on a sub-mount (40); an optical semiconductor device (1) is provided with a semiconductor laser (2) formed on a semiconductor substrate (11), an optical modulation element (4) formed on the semiconductor substrate (11), an electrostatic withstand voltage element (5) formed on the semiconductor substrate (11), and a temporary electrode (10) electrically connecting the optical modulation element (4) and the electrostatic withstand voltage element (5) in parallel. A step for electrically connecting the optical semiconductor device (1) and the drive circuit (48); and a step for electrically cutting off the temporary electrode (10) of the optical semiconductor device (1) disposed on the sub-mount (40). As a result, it is possible to provide an optical transmission device capable of performing high-speed modulation operation while improving electrostatic breakdown withstand voltage during mounting.

Description

Technical Field

[0001] The present disclosure relates to an optical semiconductor device, an optical transmission device including the optical semiconductor device, and a method for manufacturing the optical transmission device. Background Art

[0002] The modulator-integrated semiconductor laser (Electro Absorbtion Modulated Laser: EML) is an optical semiconductor device that integrates a semiconductor laser and an optical modulation element that absorbs part of the incident light by applying an electric field on the same semiconductor substrate. Compared with the direct modulation method that directly modulates the light intensity, the signal waveform is less degraded and high-speed, long-distance optical fiber transmission is possible.

[0003] As data traffic increases, the operation of the EML is required to be further accelerated. In order for the EML to modulate at high speed, it is necessary to reduce the electrostatic capacitance of the optical modulator. On the other hand, if the electrostatic capacitance of the optical modulator is reduced, the electrostatic breakdown voltage of the optical modulator is reduced. Due to the reduction in the electrostatic breakdown voltage of the optical modulator, the electrostatic breakdown voltage of the EML is also reduced, and the EML may be destroyed due to static electricity applied from a machine or an operator during the installation of the EML on a substrate or the like or during the inspection of the characteristics of the EML. Therefore, when installing and inspecting the EML, various countermeasures are implemented to remove static electricity. For example, in order to remove the static electricity of the operator, the operator wears work clothes using anti-static materials to work, or controls the humidity of the working environment and uses an ionizer to keep the working environment in an electrically neutral state. However, the above countermeasures have limits. In the case of a semiconductor device with an electrostatic breakdown voltage of approximately 100V or less, the possibility of being destroyed during installation and inspection becomes higher.

[0004] As a technology for preventing a semiconductor device from being destroyed by static electricity, Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-6548) discloses a technology for improving the electrostatic breakdown withstand voltage of a semiconductor laser by forming a withstand voltage element.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2004-6548 Summary of the invention

[0006] However, if the technology described in Patent Document 1, which is directed to semiconductor lasers, is applied to an optical modulation element of an EML, although the electrostatic breakdown withstand voltage is improved, the electrostatic capacitance of the optical modulation element increases, so there is a problem that it cannot be applied to high-speed modulation applications.

[0007] The present disclosure is made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing an optical transmission device that improves the electrostatic breakdown withstand voltage during mounting and can perform high-speed modulation operation, and an optical semiconductor device suitable therefor.

[0008] A method for manufacturing an optical transmission device comprises: a process of arranging an optical semiconductor device on a submount, the optical semiconductor device comprising a semiconductor laser formed on a semiconductor substrate, an optical modulation element formed on the semiconductor substrate, an electrostatic withstand voltage element formed on the semiconductor substrate, and a temporary electrode electrically connecting the optical modulation element and the electrostatic withstand voltage element in parallel; a process of electrically connecting the optical semiconductor device and a driving circuit; and a process of electrically disconnecting the temporary electrode of the optical semiconductor device arranged on the submount.

[0009] According to the present disclosure, it is possible to provide an optical transmission device that has an improved electrostatic breakdown withstand voltage during mounting and is capable of performing high-speed modulation operations, and an optical semiconductor device suitable therefor. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a plan view of the optical semiconductor device 1 according to the first embodiment.

[0011] Figure 2 It is a schematic cross-sectional view taken along the line AA of the optical semiconductor device 1 according to the first embodiment.

[0012] Figure 3 It is a schematic cross-sectional view taken along the line BB of the optical semiconductor device 1 according to the first embodiment.

[0013] Figure 4 It is a CC cross-sectional schematic diagram of the optical semiconductor device 1 according to the first embodiment.

[0014] Figure 5 It is a plan view of the optical semiconductor device 1 according to the first embodiment with the temporary electrode 10 cut off.

[0015] Figure 6 It is a schematic cross-sectional view taken along the line DD of the optical semiconductor device 1 according to the first embodiment with the temporary electrode 10 cut off.

[0016] Figure 7 This is an equivalent circuit diagram before static electricity is applied to the optical semiconductor device 1 according to the first embodiment.

[0017] Figure 8 This is an equivalent circuit diagram after static electricity is applied to the optical semiconductor device 1 according to the first embodiment.

[0018] Fig. 9 It is the time change of the voltage applied to the light modulation element 4 when static electricity of 100 V is applied.

[0019] Fig.10 This is a perspective view of the light transmission device in the process of arranging the optical semiconductor device on the submount.

[0020] Fig.11 This is a perspective view of the light transmission device in the process of electrically connecting the optical semiconductor device and the driving circuit.

[0021] Fig.12 This is a perspective view of the optical transmission device in the process of electrically cutting off the temporary electrodes of the optical semiconductor device disposed on the submount.

[0022] Fig.13 It is a schematic cross-sectional view of an optical semiconductor device according to a fourth embodiment.

[0023] Fig.14 It is a top view of the optical semiconductor device according to the fifth embodiment.

[0024] Fig.15 It is a top view of the optical semiconductor device according to the sixth embodiment. DETAILED DESCRIPTION

[0025] An example of the 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 and implemented without departing from the gist of the present disclosure. In addition, for convenience, parts that are repeatedly described may be omitted.

[0026] Implementation Method 1

[0027] Figure 1 It is a plan view of the optical semiconductor device 1 according to the first embodiment. Figure 2 It is a schematic cross-sectional view taken along the line AA of the optical semiconductor device 1 according to the first embodiment. Figure 3 BB is a schematic cross-sectional view of the optical semiconductor device 1 according to the first embodiment, showing a cross section of the semiconductor laser 2 . Figure 4 1 is a schematic CC cross-sectional view of the optical semiconductor device 1 according to the first embodiment, and shows cross sections of the light modulation element 4 and the electrostatic withstand voltage element 5 . Figure 5 It is a plan view of the optical semiconductor device 1 according to the first embodiment with the temporary electrode 10 cut off. Figure 6 It is a schematic cross-sectional view taken along the line DD of the optical semiconductor device 1 according to the first embodiment with the temporary electrode 10 cut off. Figure 7 is an equivalent circuit diagram before static electricity is applied to the optical semiconductor device 1 according to the first embodiment. Figure 8 This is an equivalent circuit diagram after static electricity is applied to the optical semiconductor device 1 according to the first embodiment.

[0028] First, if Figure 1 and Figure 2As shown, the optical semiconductor device 1 according to the first embodiment includes a semiconductor laser 2, a separator 3, a light modulator 4, and an electrostatic withstand voltage element 5. An anode electrode 6 is formed on the surface of the semiconductor laser 2, an anode electrode 7 is formed on the surface of the light modulator 4, and an anode electrode 9 is formed on the surface of the electrostatic withstand voltage element 5. The anode electrode 7 on the light modulator 4 is connected to a bonding pad electrode 8. In addition, the anode electrode 7 on the light modulator 4 is connected to the anode electrode 9 on the electrostatic withstand voltage element 5 via a temporary electrode 10. The semiconductor laser 2 forms a distributed feedback laser. The light modulator 4 forms an electric field absorption type semiconductor modulator, which absorbs laser light emitted from the semiconductor laser 2 by inputting an electric signal to the anode electrode 7 via the bonding pad electrode 8, thereby performing modulation. As the wavelength band of light, any wavelength band may be used as long as it is a wavelength band used in optical communication. For example, as the wavelength band of light used for optical fiber communication, there are generally short wavelength bands and long wavelength bands. As examples of the long wavelength band, a 1.3 μm band and a 1.55 μm band are used. The separator 3 separates the p-type contact layer 18a connected to the anode electrode 6 of the semiconductor laser 2 and the p-type contact layer 18b connected to the anode electrode 7 of the optical modulator 4, and electrically disconnects the semiconductor laser 2 and the optical modulator 4. The mesa strip 16 is a waveguide that is continuously formed on the semiconductor laser 2, the separator 3, and the optical modulator 4, and propagates the laser light emitted from the semiconductor laser 2. In each figure, the z direction is the direction of the optical axis of the laser light emitted from the semiconductor laser 2 (propagation direction), the x direction is a direction perpendicular to the z direction and the y direction and in which each semiconductor layer provided in the optical semiconductor device 1 extends, and the y direction is a direction perpendicular to the z direction and the x direction and in which each semiconductor layer provided in the optical semiconductor device 1 is stacked.

[0029] Next, if Figure 3As shown, the semiconductor laser 2 is formed by a stacked structure of semiconductors, and includes a semiconductor substrate 11 as an n-type InP substrate, an n-type guide layer 12, an i-type active layer 13, a diffraction grating 14, a p-type guide layer 15, a p-type InP cladding layer 17, a p-type InGaAs contact layer 18a, a buried layer 27, an insulating film 21, an anode electrode 6, and a cathode electrode 26 formed on the back side of the semiconductor substrate 11. As an example, the guide layer 12, the active layer 13, the diffraction grating 14, and the guide layer 15 use a III-V mixed crystal semiconductor such as InAlGaAs and InGaAsP, the active layer 13 uses a multiple quantum well (MQW) structure, and the buried layer 27 uses a semi-insulating InP doped with Fe. In addition, applicable semiconductors are not limited to the above-mentioned III-V mixed crystal semiconductors, and other semiconductor materials can also be applied. The surface of the contact layer 18a is covered with an insulating film 21 except for the portion where the anode electrode 6 is formed, and the anode electrode 6 is connected to the contact layer 18a via the portion where the insulating film 21 is not formed. The anode electrode 6 is composed of a first electrode layer 22 in contact with the contact layer 18a as a semiconductor layer, and a second electrode layer 23 formed on the first electrode layer 22. The first electrode layer 22 not only improves the adhesion with the contact layer 18a, but also has a function as a barrier metal that inhibits the metal of the second electrode layer 23 from diffusing into the contact layer 18a. As an example of the first electrode layer 22 and the second electrode layer 23, the first electrode layer 22 uses an electrode structure in which Ti / Pt / Au is sequentially formed from the layer in contact with the contact layer 18a, and the second electrode layer 23 uses an electrode structure in which Au is formed. The cathode electrode 26 is composed of a first electrode layer 24 and a second electrode layer 25. The first electrode layer 24 not only improves the adhesion with the semiconductor substrate 11, but also has a function as a barrier metal that inhibits the metal of the second electrode layer 25 from diffusing into the semiconductor substrate 11. As an example of the first electrode layer 24 and the second electrode layer 25, the first electrode layer 24 uses an electrode structure in which AuGe / Ni / Ti / Pt / Au is sequentially used from the layer in contact with the semiconductor substrate 11, and the second electrode layer 25 uses an electrode structure in which Au is used. In addition, the electrode structures of the first electrode layer 22, the second electrode layer 23, the first electrode layer 24, and the second electrode layer 25 are not limited to the above combination, and any combination can be applied.

[0030] Next, if Figure 4As shown, the optical modulation element 4 is formed by a semiconductor stacking structure, and includes a semiconductor substrate 11, a guide layer 12, an i-type light absorbing layer 20, a guide layer 15, a cladding layer 17, a buried layer 27, a p-type InGaAs contact layer 18b, an insulating film 21, an anode electrode 7, and a cathode electrode 26. As an example, the light absorbing layer 20 uses an MQW structure composed of a III-V mixed crystal semiconductor such as InAlGaAs and InGaAsP. In addition, the applicable semiconductor is not limited to the above-mentioned III-V mixed crystal semiconductor, and other semiconductor materials can be applied. The surface of the contact layer 18b is covered with an insulating film 21 except for the portion where the anode electrode 7 is formed, and the anode electrode 7 is connected to the contact layer 18b via the portion where the insulating film 21 is not formed. The anode electrode 7 is composed of a first electrode layer 22 in contact with the contact layer 18b as a semiconductor layer, and a second electrode layer 23 formed on the first electrode layer 22. Generally, the optical modulator 4 is narrow in order to confine light to the mesa strips 16, so the width of the anode electrode 7 formed directly above it is also narrow. Therefore, the bonding pad electrode 8 with a large area is connected to the anode electrode 7, and the modulation signal is input to the optical modulator 4 via the bonding pad electrode 8.

[0031] Next, if Figure 4 As shown, the electrostatic withstand voltage element 5 is formed of a semiconductor stacked structure, and includes a semiconductor substrate 11, a guide layer 12, a light absorbing layer 20, a guide layer 15, a cladding layer 17, a contact layer 18b, an insulating film 21, an anode electrode 9, and a cathode electrode 26. The surface of the contact layer 18b is covered with an insulating film 21 except for a portion where the anode electrode 9 is formed, and the anode electrode 9 is connected to the contact layer 18b via a portion where the insulating film 21 is not formed. The anode electrode 9 is composed of a first electrode layer 22 in contact with the contact layer 18b as a semiconductor layer, and a second electrode layer 23 formed on the first electrode layer 22. The anode electrode 9 is connected to the anode electrode 7 on the optical modulator 4 via a temporary electrode 10. The electrostatic withstand voltage element 5 and the optical modulator 4 have at least a part of the same layer structure and can be formed by the same manufacturing process. Here, "the same layer structure" means that the thickness and composition of the two layer structures are the same. When the two layer structures are multilayer structures, it means that the thickness and composition of each layer constituting the multilayer structure are the same. In addition, the electrostatic withstand voltage element 5 can be in any shape when viewed from above as long as it is electrically connected to the light modulation element 4. Figure 1 In the figure, the top view shape of the anode electrode 9 of the electrostatic withstand voltage element 5 is shown as a rectangular example, but it is not limited to this, and it can also be an ellipse, etc. In addition, since the electrostatic capacitance of the electrostatic withstand voltage element 5 is larger, the effect of improving the electrostatic breakdown withstand voltage is greater, so the larger the area of ​​the top view shape, that is, the anode electrode 9, the greater the effect of improving the electrostatic breakdown withstand voltage.

[0032] Next, the operation of the optical semiconductor device 1 according to Embodiment 1 will be described. The driving method of the optical semiconductor device 1 described below is an example, and various changes can be made within the scope of the present disclosure.

[0033] First, in the semiconductor laser 2, a voltage is applied between the anode electrode 6 and the cathode electrode 26 to generate recombination of electrons and holes, and light is generated by the recombination. The generated light is reflected by the diffraction grating 14 and reciprocates in the semiconductor laser 2. Stimulated emission occurs during the reciprocation, and the intensity of the light is amplified. If a certain threshold is reached, laser oscillation occurs, and laser light is emitted from the semiconductor laser 2 toward the light modulator 4. In the light modulator 4, if a negative voltage is applied from the anode electrode 7 to the cathode electrode 26 via the bonding pad electrode 8, light absorption occurs due to the quantum confined Stark effect of the light absorption layer 20. That is, the intensity of the laser light emitted from the light modulator 4 is modulated corresponding to the voltage value applied to the light modulator 4. The modulated laser light is emitted to the outside of the optical semiconductor device 1 and used as a signal light in optical communication. In addition, the upper limit of the modulation speed is mainly in inverse proportion to the electrostatic capacitance of the light modulator 4, so the capacity of the light modulator 4 for high-speed modulation purposes is extremely small.

[0034] Here, it is assumed that a voltage caused by static electricity is applied to the light modulator 4. Due to the application of the voltage caused by static electricity, current flows to the light modulator 4, but since the electrostatic withstand voltage element 5 is connected in parallel with the light modulator 4, part of the current is distributed to the electrostatic withstand voltage element 5. Since part of the current flows to the electrostatic withstand voltage element 5, the voltage applied to the light modulator 4 decreases, and the electrostatic breakdown withstand voltage of the light modulator 4 increases.

[0035] Next, an equivalent circuit diagram using a human body model (HBM) is shown in FIG. Figure 7 and Figure 8 This equivalent circuit is composed of a voltage source 28, a protection resistor 30, a discharge capacitor 29, a discharge resistor 32, a switch 31, an electrostatic capacitor 33 of the light modulation element 4, and an electrostatic capacitor 34 of the electrostatic withstand voltage element 5. First, as Figure 7 As shown in FIG. 1 , before static electricity is applied to the optical semiconductor device, that is, the state in which the human body is charged with static electricity, the charge is charged to the discharge capacitor 29 via the voltage source 28. Figure 8As shown, the state where static electricity is applied to the optical semiconductor is represented as a circuit in which the switch 31 is switched from the protection resistor 30 side to the discharge resistor 32 side. When the switch 31 is switched, the charge charged in the discharge capacitor 29 flows to the optical modulation element 4 and the electrostatic withstand voltage element 5. At this time, the voltage 35 applied to the optical modulation element 4 is determined by the ratio of the combined capacitance of the electrostatic capacitor 33 and the electrostatic capacitor 34 to the discharge capacitor 29. The larger the combined capacitance, the lower the voltage 35 applied to the optical modulation element 4.

[0036] here, Fig. 9 FIG. 4 shows an example of a time change of the voltage applied to the light modulator 4 when static electricity of 100 V is applied. Fig. 9 In the figure, the dotted line indicates the case where there is no electrostatic withstand voltage element 5, and the solid line indicates the case where the electrostatic withstand voltage element 5 is connected in parallel with the optical modulator 4. In HBM, the discharge capacitor 29 is 100pF and the discharge resistor 32 is 1.5kΩ. For example, in the case of an optical semiconductor device with a modulation speed of 100Gbps, the electrostatic capacitance 33 of the optical modulator 4 is extremely small, about 0.1pF, so in the case where there is no electrostatic withstand voltage element 5, the voltage 35 applied to the optical modulator 4 is 100V, and the optical modulator 4 is destroyed by static electricity assuming that the electrostatic breakdown voltage of the optical modulator 4 is 80V. On the other hand, when a 50pF electrostatic withstand voltage element 5 is connected in parallel with the optical modulator 4, the combined capacitance is 50.1pF, and the voltage 35 applied to the optical modulator 4 is reduced to about 67V. Assuming that the electrostatic withstand voltage of the optical modulator 4 is 80V, by connecting the electrostatic withstand voltage element 5 in parallel, it is possible to prevent the optical modulator 4 from being destroyed by static electricity.

[0037] The optical semiconductor device 1 according to the first embodiment is characterized in that the electrical connection between the electrostatic withstand voltage element 5 for improving the electrostatic breakdown withstand voltage and the optical modulation element 4 can be cut off. During the installation of the optical semiconductor device on a substrate or the like, or during the inspection of the characteristics of the optical semiconductor device, the electrostatic withstand voltage element is useful in order to prevent the semiconductor element of the optical semiconductor device from being damaged by static electricity applied from a machine or an operator, but after being installed in an optical transmission device such as a transceiver with a built-in electrostatic protection circuit, the electrostatic withstand voltage element becomes unnecessary. Rather, in a semiconductor device that performs high-speed modulation, it is necessary to reduce the electrostatic capacitance of the part related to high-speed operation represented by the modulation element, and it is not preferable that the capacitance of the electrostatic withstand voltage element is added to the modulation element. That is, when installing and inspecting an optical semiconductor device that needs to improve the electrostatic breakdown withstand voltage, it is necessary to electrically connect the electrostatic withstand voltage element, and after being installed in an optical transmission device such as a transceiver, it is necessary to electrically separate the electrostatic withstand voltage element. The first embodiment is an optical semiconductor device that meets this purpose. Figure 5 is Figure 1A top view of the optical semiconductor device 1 according to the first embodiment shown in FIG. 1 in which the electrical connection between the light modulation element 4 and the electrostatic withstand voltage element 5 is separated, Figure 6 It is along Figure 5 FIG. 4 is a schematic cross-sectional view of the light modulation element 4 and the electrostatic withstand voltage element 5 cut along the dotted line DD. Figure 1 In the embodiment, the light modulator 4 and the electrostatic withstand voltage element 5 are electrically connected via the temporary electrode 10, so in order to separate their electrical connection, the temporary electrode 10 can be removed. The optical semiconductor device 1 involved in embodiment 1 is characterized in that since the light modulator 4 and the electrostatic withstand voltage element 5 are electrically connected via the temporary electrode 10, it is easy to cut the electrical connection between the two, for example, compared with the case where the two are formed by one electrode. As a method of separating the electrical connection, there is a method of cutting the temporary electrode 10 by scratching or laser trimming, but it is not limited to the exemplified method, and a method of dissolving the temporary electrode 10 by heat treatment or liquid treatment can also be arbitrarily applied. After being installed in an optical transmission device such as a transceiver, the temporary electrode 10 is cut off, and it is set Figure 5 and Figure 6 With the structure shown, the influence of the capacitance of the electrostatic withstand voltage element 5 on the light modulation element 4 disappears, and the optical semiconductor device 1 can operate as a semiconductor device that performs high-speed modulation.

[0038] Next, the effect of embodiment 1 is explained by comparing it with the prior art document. Patent document 1 is a structure in which the electrical connection between the semiconductor laser and the electrostatic withstand voltage element cannot be cut off. When the electrostatic withstand voltage element is provided in the same manner as the optical modulator, the electrostatic capacitance of the electrostatic withstand voltage element is added to the optical modulator. As a result, the electrostatic capacitance of the optical modulator increases and high-speed operation cannot be performed, so it cannot be used for high-speed modulation purposes. On the other hand, in the technology disclosed in the present invention, the electrostatic breakdown withstand voltage of the optical modulator can be improved without complicating the manufacturing process and adding components, and the electrical connection between the electrostatic withstand voltage element and the optical modulator is then separated, so it can also be applied to optical semiconductor devices that perform high-speed modulation.

[0039] Next, a method for manufacturing the optical semiconductor device 1 is briefly described. An n-type guide layer 12 is crystal-grown on the surface of the semiconductor substrate 11 using the MOCVD (Metal Organic Chemical Vapor Deposition) method. On the surface of the guide layer 12, in each region of the semiconductor laser 2, the separation portion 3, and the optical modulation element 4, an active layer 13, a light absorption layer 20, a diffraction grating 14, and a p-type guide layer 15 are formed by crystal growth using the MOCVD method and dry etching using a SiO2 mask. On the surface of the guide layer 15, a SiO2 mask having the same shape as the surface shape of the mesa strip 16 is formed, and the mesa strip 16 is formed by dry etching using the SiO2 mask. Thereafter, a buried layer 27 is crystal-grown on the exposed portions on both sides of the mesa strip 16. The SiO2 mask is removed, and the p-type cladding layer 17, contact layer 18a, and contact layer 18b are crystal-grown in sequence on the surfaces of the buried layer 27 and the mesa strip 16. The contact layer 18b on the separation portion 3 is removed by wet etching using a photoresist mask.

[0040] Next, an insulating film 21 of SiN, SiO2 or the like is formed on the surface of the semiconductor laser 2, the separator 3, and the light modulator 4 by a plasma CVD method or the like. For the region where the electrode is to be formed, an opening is formed in the insulating film 21 by combining a photolithography technique and an etching technique using fluoric acid or the like. Thereafter, a first electrode layer 22 of a Ti / Pt / Au structure and a second electrode layer 23 including an Au layer are sequentially formed from the semiconductor layer side. As a formation method, an electron beam evaporation method, a plating method or the like is used to peel off unnecessary portions together with the photoresist film, thereby forming an anode electrode 6, an anode electrode 7, and an anode electrode 9 having a first electrode layer 22 and a second electrode layer 23 in the opening of the insulating film 21. At this time, a bonding pad electrode 8 connected to the anode electrode 7 and a temporary electrode 10 connecting the anode electrode 7 and the anode electrode 9 are simultaneously formed. Thereafter, the lower surface of the semiconductor substrate 11 is polished, and a cathode electrode 26 is formed on the lower surface of the semiconductor substrate 11. The cathode electrode 26 is composed of a first electrode layer 24 of AuGe / Ni / Ti / Pt / Au structure and a second electrode layer 25 including an Au layer. In addition, the electrode structure of the first electrode layer 22, the second electrode layer 23, the first electrode layer 24, and the second electrode layer 25 shown here is an example, and the electrode structure is not limited. Any electrode structure can be applied without departing from the scope of the present disclosure. The optical semiconductor device 1 involved in embodiment 1 can be manufactured through the above process.

[0041] The materials shown in Embodiment 1 are just examples and are not limited thereto. In addition, the active layer 13 and the light absorbing layer 20 are configured as MQW structures, but the quantum well layer may be a single layer or may not be a quantum well. Figure 2In the invention, it is described that the separator 3 and the light modulator 4 are formed by stacking the same semiconductor layers, but they may also be formed by semiconductors of different compositions. Figure 2 In the example, the diffraction grating 14 is formed on the active layer 13, but it can also be formed below the active layer 13. In addition, the example in which the cladding layer 17, the contact layer 18a, and the contact layer 18b are formed in common in the regions of the semiconductor laser 2, the separator 3, and the light modulator 4 is shown, but they can also be formed independently through different processes. Figure 4 In the embodiment, the electrostatic withstand voltage element 5 and the light modulating element 4 are structured in the same layer, but the electrostatic withstand voltage element 5 and the semiconductor laser 2 may also be structured in the same layer. Figure 1 In the example described above, the widths of the mesa strips 16 of the semiconductor laser 2, the separator 3, and the light modulator 4 are the same, but the widths of the mesa strips 16 may be different. Figure 3 , Figure 4 In the embodiment, the semiconductor laser 2 and the light modulator 4 are provided with an embedded structure, but may also be other structures such as a ridge structure. In addition, the anode electrode 7 of the light modulator 4 and the anode electrode 9 of the electrostatic withstand voltage element 5 may be connected by wire bonding instead of the temporary electrode 10 connecting the anode electrode 7 of the light modulator 4 and the anode electrode 9 of the electrostatic withstand voltage element 5.

[0042] Next, a method for manufacturing an optical transmission device to which the optical semiconductor device 1 is applied will be described.

[0043] A method for manufacturing an optical transmission device using an optical semiconductor device 1 includes a step of placing the optical semiconductor device on a submount, a step of electrically connecting the optical semiconductor device and a drive circuit, and a step of electrically disconnecting a temporary electrode of the optical semiconductor device placed on the submount. Fig.10 , Fig.11 , Fig.12 The light transmission device in each manufacturing process is shown in FIG. Fig.10 This is a perspective view of the optical transmission device in the process of arranging the optical semiconductor device on the submount. Fig.11 This is a perspective view of the optical transmission device in the process of electrically connecting the optical semiconductor device and the driving circuit. Fig.12 This is a perspective view of the optical transmission device in the process of electrically cutting off the temporary electrodes of the optical semiconductor device disposed on the submount.

[0044] First, in the process of placing the optical semiconductor device on the submount, Fig.10As shown, the optical semiconductor device 1 is arranged on the submount 40 of the optical transmission device 49. As a method of arranging it on the submount 40, for example, die bonding is performed using solder. The submount 40 has signal lines 42 and 43 for transmitting electrical signals, and is die-fixed to the substrate 41. Generally speaking, the substrate 41 functions as a heat sink for dissipating the heat generated by the optical semiconductor device 1 to the outside, or as a thermoelectric controller for adjusting the temperature of the optical semiconductor device 1. In addition, on the substrate 41, there is a drive circuit 48 for inputting and outputting electrical signals to and from the optical semiconductor device 1. The drive circuit 48 includes not only the optical semiconductor device 1, but also an electrical circuit for controlling the thermoelectric controller of the substrate 41, a circuit for preventing electrostatic discharge (ESD) to the optical semiconductor device 1, and the like. In addition, a photodiode element for monitoring the light output of the optical semiconductor device 1 is also mounted on the submount 40 or the substrate 41, but the illustration and description are omitted.

[0045] Next, in the process of electrically connecting the optical semiconductor device and the driving circuit, Fig.11 As shown, wire wiring for inputting and outputting electrical signals between the drive circuit 48 and the optical semiconductor device 1 is performed. First, wire bonding is performed from the bonding pad electrode 8 connected to the optical modulation element 4 of the optical semiconductor device 1 to the signal line 42 on the submount 40. Next, wire bonding is performed from the anode electrode 6 of the semiconductor laser 2 of the optical semiconductor device 1 to the signal line 43 on the submount 40. Next, wire bonding is performed from the signal lines 42 and 43 to the drive circuit 48. Among them, Au wires are used as the leads for the wire wiring, but this is not limited to this. In addition, the order of performing the wire bonding is not limited to the above order.

[0046] Next, in the step of electrically cutting off the temporary electrodes of the optical semiconductor device disposed on the submount, Fig.12 As shown, by cutting the temporary electrode 10, the electrical connection between the optical modulator 4 and the electrostatic withstand voltage element 5 is separated. By configuring the lead 44 and the lead 46, the optical modulator 4 is connected to the ESD protection circuit of the drive circuit 48, so the electrostatic withstand voltage element 5 becomes unnecessary. As a method for cutting the temporary electrode 10, for example, it is scraped with a probe to peel it off, and the electrical connection between the optical modulator 4 and the electrostatic withstand voltage element 5 is separated. As a method for cutting the temporary electrode 10, it is not limited to scraping, and a cutting method corresponding to the material and shape of the temporary electrode 10 can also be applied. For example, a method of cutting by laser trimming can also be applied. By cutting the temporary electrode 10, the capacitance of the electrostatic withstand voltage element 5 is electrically separated from the optical modulator 4. Therefore, it is possible to provide an optical transmission device 49 capable of high-speed modulation operation.

[0047] By applying the manufacturing method of the optical transmission device constructed in this way, after the optical semiconductor device is installed in the optical transmission device, the temporary electrode of the optical semiconductor device can be cut off, so that an optical transmission device that uses an optical semiconductor device with improved electrostatic breakdown voltage resistance of the optical modulation element and can perform high-speed modulation operations can be provided.

[0048] As described above, the optical semiconductor device of embodiment 1 is an optical semiconductor device comprising a semiconductor laser formed on a semiconductor substrate, an optical modulator formed on a semiconductor substrate, an electrostatic withstand voltage element formed on a semiconductor substrate, and a temporary electrode that electrically connects the optical modulator and the electrostatic withstand voltage element in parallel, and separates the electrostatic capacitor of the electrostatic withstand voltage element from the optical modulator by electrically cutting off the temporary electrode.

[0049] The optical semiconductor device constructed in this way can improve the electrostatic breakdown withstand voltage of the optical modulator element. Furthermore, after being installed in the optical transmission device, the temporary electrode can be cut off, so that the electrostatic capacitance of the electrostatic withstand voltage element can be separated from the electrostatic capacitance of the optical modulator element, so that the optical semiconductor device and the optical transmission device equipped with the same can be operated for high-speed modulation purposes.

[0050] Therefore, by applying the optical semiconductor device described in Embodiment 1, it is possible to provide an optical transmission device that has an improved electrostatic breakdown withstand voltage during mounting and can perform a high-speed modulation operation, and an optical semiconductor device suitable therefor.

[0051] Implementation Method 2

[0052] The optical semiconductor device of the second embodiment is different from the first embodiment in that the first electrode layer of the temporary electrode 10 does not contain Ti. As a technology applied to the electrode of the semiconductor device, it is known that the adhesion between the electrode and the object on which the electrode is formed is improved by containing Ti in the lower layer of the electrode. That is, by not containing Ti in the first electrode layer corresponding to the lower layer of the temporary electrode 10, the adhesion between the temporary electrode 10 and the insulating film 21 becomes weaker than when containing Ti, and the temporary electrode 10 can be cut more easily.

[0053] By using the optical semiconductor device configured in this way, it is possible to improve the electrostatic breakdown withstand voltage of the optical modulator 4. Furthermore, after being mounted in the optical transmission device, the temporary electrode 10 can be cut more easily, so that the electrostatic capacitance of the electrostatic withstand voltage element 5 can be separated from the electrostatic capacitance of the optical modulator 4, so that it can be operated for high-speed modulation.

[0054] Therefore, by applying the optical semiconductor device shown in embodiment 2, the electrostatic breakdown withstand voltage during installation can be improved and the electrostatic capacitance of the electrostatic withstand voltage element can be more easily separated from the electrostatic capacitance of the optical modulation element, so that an optical transmission device capable of high-speed modulation operations and an optical semiconductor device suitable therefor can be provided.

[0055] Implementation 3

[0056] The optical semiconductor device of the third embodiment is different from the first embodiment in that the first electrode layer of the anode electrode 9 of the electrostatic withstand voltage element 5 does not contain Ti. Since the first electrode layer corresponding to the lower layer of the anode electrode 9 does not contain Ti, the adhesion between the anode electrode 9 and the contact layer 18b becomes weaker than when Ti is contained, and the anode electrode 9 can be peeled off more easily. For example, the anode electrode 9 can be torn off by clamping the end of the anode electrode 9 of the electrostatic withstand voltage element 5 with tweezers and lifting it from the semiconductor surface. In particular, since it can be imagined that the anode electrode 9 of the electrostatic withstand voltage element 5 is formed with as large an area as possible, the workability is improved compared with the case of directly cutting the temporary electrode 10 as in the first embodiment. In addition, since the removal of the anode electrode 9 substantially corresponds to the cutting of the temporary electrode 10, the same effect as the case of directly cutting the temporary electrode 10 can be obtained.

[0057] In addition, in addition to making the first electrode layer of the temporary electrode 10 free of Ti as in embodiment 2, the first electrode layer of the anode electrode 9 is also made free of Ti, so that the anode electrode 9 and the temporary electrode 10 can be peeled off together, and the electrostatic capacitance of the electrostatic withstand voltage element 5 can be separated from the electrostatic capacitance of the optical modulator element 4 more easily and efficiently.

[0058] By using the optical semiconductor device configured in this way, it is possible to improve the electrostatic breakdown withstand voltage of the optical modulator 4. Furthermore, after being mounted in the optical transmission device, the temporary electrode 10 can be cut more easily and efficiently, so that the electrostatic capacitance of the electrostatic withstand voltage element 5 can be separated from the electrostatic capacitance of the optical modulator 4, so that it can be operated for high-speed modulation purposes.

[0059] Therefore, by applying the optical semiconductor device shown in embodiment 3, it is possible to improve the electrostatic breakdown voltage resistance during installation, and to more easily and efficiently separate the electrostatic capacitance of the electrostatic voltage-resistant element from the electrostatic capacitance of the optical modulation element, thereby providing an optical transmission device capable of high-speed modulation operations and an optical semiconductor device suitable therefor.

[0060] Implementation 4

[0061] Fig.13 It is a schematic cross-sectional view of an optical semiconductor device according to a fourth embodiment.

[0062] The optical semiconductor device of the fourth embodiment is different from the first embodiment in that the temporary electrode 10 is composed of a metal film 19 having a lower melting point than the metal film constituting the anode electrode 7 of the optical modulation element 4. The other basic effects are the same as those of the first embodiment, but the electrical connection between the optical modulation element 4 and the electrostatic withstand voltage element 5 can be cut more easily than that of the first embodiment. Specifically, a current flows from the bonding pad electrode 8 of the optical modulation element 4 toward the anode electrode 9 of the electrostatic withstand voltage element 5 or in the opposite direction, and the temporary electrode 10 having a low melting point is melted by the generated Joule heat, thereby cutting off the electrical connection between the optical modulation element 4 and the electrostatic withstand voltage element 5. The metal film 19 constituting the temporary electrode 10 can be arbitrarily selected according to the relative relationship between the melting point and the other electrodes, for example, represented by AuSn solder. In addition, the current value for melting the temporary electrode 10 can be adjusted by adjusting not only the material of the metal film 19 but also the cross-sectional area, length, etc.

[0063] By using the optical semiconductor device configured in this way, it is possible to improve the electrostatic breakdown withstand voltage of the optical modulator 4. Furthermore, after being mounted in the optical transmission device, the temporary electrode 10 can be easily cut off by heat, so that the electrostatic capacitance of the electrostatic withstand voltage element 5 can be separated from the electrostatic capacitance of the optical modulator 4, so that it can be operated for high-speed modulation.

[0064] Therefore, by applying the optical semiconductor device shown in embodiment 4, the electrostatic breakdown voltage resistance during installation can be improved, and the electrostatic capacitance of the electrostatic voltage resistance element can be easily separated from the electrostatic capacitance of the optical modulation element by heat, so that an optical transmission device capable of high-speed modulation operations and an optical semiconductor device suitable therefor can be provided.

[0065] Implementation method 5

[0066] Fig.14 It is a top view of the optical semiconductor device according to the fifth embodiment.

[0067] The optical semiconductor device 36 shown in the fifth embodiment is different from the first embodiment in that the anode electrode 7 of the optical modulator 4 and the anode electrode 6 of the semiconductor laser 2 are connected at the temporary electrode 37. By connecting the anode electrode 7 of the optical modulator 4 and the anode electrode 6 of the semiconductor laser 2, the semiconductor laser 2 can function as an electrostatic withstand voltage element in the optical semiconductor device 36 even if an electrostatic withstand voltage element is not formed separately. This is particularly effective when the optical semiconductor device is not inspected for characteristics before being mounted on an optical transmission device such as a transceiver. Compared with the first, second, third, and fourth embodiments, it is not necessary to form an anode electrode of the electrostatic withstand voltage element, so the material cost of the electrode can be low.

[0068] By using the optical semiconductor device configured in this way, it is possible to improve the electrostatic breakdown withstand voltage of the optical modulator 4 without forming an electrostatic withstand voltage element separately. Furthermore, after being mounted in the optical transmission device, the temporary electrode 37 can be cut off, so that the electrostatic capacitance of the semiconductor laser 2 can be separated from the electrostatic capacitance of the optical modulator 4, so that it can be operated for high-speed modulation purposes.

[0069] Therefore, by applying the optical semiconductor device described in Embodiment 5, it is possible to provide an optical transmission device that can improve the electrostatic breakdown withstand voltage during mounting and perform high-speed modulation operation without separately forming an electrostatic withstand voltage element, and an optical semiconductor device suitable therefor.

[0070] Implementation 6

[0071] Fig.15 It is a top view of the optical semiconductor device according to the sixth embodiment.

[0072] The optical semiconductor device 38 shown in the sixth embodiment is different from the first embodiment in that the anode electrode 9 of the electrostatic withstand voltage element 5 and the anode electrode 6 of the semiconductor laser 2 are connected by a temporary electrode 39. The fact that the anode electrode 9 of the electrostatic withstand voltage element 5 and the anode electrode 6 of the semiconductor laser 2 are connected by the temporary electrode 39 means that both the semiconductor laser 2 and the electrostatic withstand voltage element 5 different from the semiconductor laser 2 function as electrostatic withstand voltage elements. That is, since the anode electrode 9 of the electrostatic withstand voltage element 5 and the anode electrode 6 of the semiconductor laser 2 are connected by the temporary electrode 39, the light modulation element 4 is connected to the electrostatic capacitance of the electrostatic withstand voltage element 5 and the electrostatic capacitance of the semiconductor laser 2, so that the electrostatic breakdown withstand voltage can be further improved compared with the case where only one of the elements is connected.

[0073] By using the optical semiconductor device thus constructed, the electrostatic breakdown withstand voltage of the optical modulator 4 can be further improved compared to Embodiment 1. Furthermore, after being mounted in the optical transmission device, the temporary electrode 10 can be cut off, so that the electrostatic withstand voltage element 5 and the electrostatic capacitance of the semiconductor laser 2 can be separated from the electrostatic capacitance of the optical modulator 4, so that it can be operated for high-speed modulation purposes.

[0074] Therefore, by applying the optical semiconductor device described in Embodiment 6, it is possible to provide an optical transmission device that has a further improved electrostatic breakdown withstand voltage during mounting and can perform high-speed modulation operations, and an optical semiconductor device suitable therefor.

[0075] Modification of Implementation Example 6

[0076] In the sixth embodiment, an example is shown in which the temporary electrode 39 connects the anode electrode 9 of the electrostatic withstand voltage element 5 and the anode electrode 6 of the semiconductor laser 2. However, as a modified example, the temporary electrode 39 may connect the anode electrode 6 of the semiconductor laser 2 and the anode electrode 7 or the bonding pad electrode 8 of the optical modulator 4. That is, the temporary electrode 39 may connect the anode electrode 7 or the bonding pad electrode 8 of the optical modulator 4 and the anode electrode 6 of the semiconductor laser 2 without passing through the anode electrode 9 of the electrostatic withstand voltage element 5. In this case, both the semiconductor laser 2 and the electrostatic withstand voltage element 5 different from the semiconductor laser 2 function as electrostatic withstand voltage elements as in the sixth embodiment, and even if one of the electrostatic withstand voltage element 5 and the semiconductor laser 2 does not function as an electrostatic withstand voltage element, one of them can function as an electrostatic withstand voltage element, so that the manufacturing yield can be improved.

[0077] By using the optical semiconductor device constructed in this way, it is possible to improve the yield rate and increase the electrostatic breakdown withstand voltage of the optical modulator 4. Furthermore, after being installed in the optical transmission device, the temporary electrodes 10 and 39 can be cut off, so that the electrostatic withstand voltage element 5 and the electrostatic capacitance of the semiconductor laser 2 can be separated from the electrostatic capacitance of the optical modulator 4, so that it can be operated for high-speed modulation purposes.

[0078] Therefore, by applying the optical semiconductor device shown in the variation of embodiment 6, it is possible to provide an optical transmission device that improves the yield and the electrostatic breakdown withstand voltage during mounting and can perform high-speed modulation operations, and an optical semiconductor device suitable therefor.

[0079] In addition, the present disclosure can freely combine the various embodiments within a range that does not contradict each other, and can appropriately modify or omit the various embodiments.

[0080] Description of Reference Numerals

[0081] 1…optical semiconductor device; 2…semiconductor laser; 3…separator; 4…optical modulator; 5…electrostatic withstand voltage element; 6…anode electrode; 7…anode electrode; 8…bonding pad electrode; 9…anode electrode; 10…temporary electrode; 11…semiconductor substrate; 12…guiding layer; 13…active layer; 14…diffraction grating; 15…guiding layer; 16…table strip; 17…cladding layer; 18a…contact layer; 18b…contact layer; 19…metal film; 20…light absorption layer; 21…insulating film; 22…first electrode layer; 23…second electrode layer; 24…first electrode layer electrode layer; 25…second electrode layer; 26…cathode electrode; 27…buried layer; 28…voltage source; 29…discharge capacitor; 30…protection resistor; 31…switch; 32…discharge resistor; 33…electrostatic capacitor; 34…electrostatic capacitor; 35…voltage; 36…optical semiconductor device; 37…temporary electrode; 38…optical semiconductor device; 39…temporary electrode; 40…submount; 41…substrate; 42…signal line; 43…signal line; 44…lead; 45…lead; 46…lead; 47…lead; 48…drive circuit; 49…optical transmission device.

Claims

1. A method for manufacturing an optical transmission device, characterized in that: have: The step of arranging an optical semiconductor device on a submount, the optical semiconductor device comprising a semiconductor laser formed on a semiconductor substrate, a light modulation element formed on the semiconductor substrate, an electrostatic withstand voltage element formed on the semiconductor substrate, and a temporary electrode electrically connecting the light modulation element and the electrostatic withstand voltage element in parallel; A step of electrically connecting the optical semiconductor device and a driving circuit; as well as and a step of electrically disconnecting the temporary electrode of the optical semiconductor device disposed on the submount.

2. An optical semiconductor device, characterized in that: have: Semiconductor lasers are formed on semiconductor substrates; A light modulation element formed on the semiconductor substrate; An electrostatic withstand voltage element is formed on the semiconductor substrate; as well as A temporary electrode electrically connects the light modulation element and the electrostatic withstand voltage element in parallel, The electrostatic capacitance of the electrostatic withstand voltage element is separated from the light modulation element by electrically cutting off the temporary electrode.

3. The optical semiconductor device according to claim 2, wherein: The first electrode layer of the temporary electrode is composed of a metal that does not contain Ti.

4. The optical semiconductor device according to claim 2 or 3, characterized in that The first electrode layer of the anode electrode of the electrostatic withstand voltage element is made of a metal that does not contain Ti.

5. The optical semiconductor device according to any one of claims 2 to 4, characterized in that: The temporary electrode is made of a metal having a lower melting point than a metal constituting the anode electrode of the light modulation element.

6. The optical semiconductor device according to any one of claims 2 to 5, wherein: The electrostatic withstand voltage element is the semiconductor laser.

7. The optical semiconductor device according to any one of claims 2 to 6, wherein: The electrostatic withstand voltage element includes the semiconductor laser and an electrostatic withstand voltage element different from the semiconductor laser.

8. The optical semiconductor device according to claim 7, wherein The anode electrode of the semiconductor laser is connected to the anode electrode of the light modulation element via the anode electrode of an electrostatic withstand voltage element different from the semiconductor laser.

9. The optical semiconductor device according to claim 7, wherein: The anode electrode of the semiconductor laser is connected to the anode electrode of the light modulation element without passing through an anode electrode of an electrostatic withstand voltage element different from the semiconductor laser.

10. An optical transmission device, characterized in that: have: The optical semiconductor device according to any one of claims 2 to 9; and The drive circuit is electrically connected to the optical semiconductor device.

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