JP6578730B2 - Optical semiconductor device, method for manufacturing optical semiconductor device, and method for inspecting optical semiconductor device - Google Patents

Description

  The present invention relates to an optical semiconductor device, an optical semiconductor device manufacturing method, and an optical semiconductor device inspection method.

  In a Mach-Zehnder modulator formed of a high-mesa waveguide, a structure in which the entire waveguide is embedded with BCB resin is disclosed for the purpose of surface flattening, capacity reduction, and the like (see, for example, Patent Document 1).

JP2013-096268A

  However, when an optical semiconductor element such as a Mach-Zehnder modulator is used, laser light having a high light intensity is incident on the waveguide as input light from the outside. If the input light deviates from the waveguide and is focused on the resin, the resin is decomposed and vaporized by the high energy of the laser light, and there is a possibility that a failure to reattach to the end face may occur. The reattached resin causes light absorption and scattering. As a result, optical loss may increase, leading to a decrease in incidence efficiency.

  Then, it aims at providing the optical semiconductor element which can suppress decomposition | disassembly and vaporization of resin, the manufacturing method of an optical semiconductor element, and the inspection method of an optical semiconductor element.

  An optical semiconductor device according to the present invention includes a waveguide formed on a substrate and defined by a side surface and an upper surface and having an end surface, and a resin that embeds the waveguide on the substrate, and the side surface of the waveguide and The non-resin area | region where the said resin is not provided in the upper surface is an optical semiconductor element extended over a predetermined distance from the said end surface in the direction where the said waveguide is extended.

  In the method for manufacturing an optical semiconductor device according to the present invention, a waveguide defined by a side surface and an upper surface and having an end surface is formed on a substrate, the waveguide is embedded on the substrate with a resin, and the waveguide is formed from the end surface. This is a method for manufacturing an optical semiconductor element, in which the resin is removed over a predetermined distance in the extending direction.

  An optical semiconductor device inspection method according to the present invention comprises: a semiconductor waveguide formed on a substrate, defined by a side surface and an upper surface, and having an end surface; and a resin for embedding the waveguide on the substrate, An inspection method of an optical semiconductor device in which a non-resin region in which the resin is not provided on a side surface and an upper surface of a waveguide extends over a predetermined distance from the end surface in a direction in which the waveguide extends, and by causing light to enter the end surface It is an inspection method for an optical semiconductor element, in which an electrical signal obtained from the waveguide is measured.

  According to the said invention, decomposition | disassembly and vaporization of resin can be suppressed.

It is a perspective view of the optical waveguide part of the modulator which concerns on a comparative example. It is a perspective view containing resin which covers an optical waveguide part. It is a perspective view of the modulator 0 which concerns on embodiment. (A) is an end view of the input waveguide, and (b) is a top view of the periphery of the input waveguide. It is a perspective view of the modulator concerning a modification. (A)-(f) is a manufacturing flowchart in the optical waveguide periphery. FIG. 7 is a manufacturing flow diagram after FIG. FIG. 7 is a manufacturing flow diagram after FIG. It is the schematic of the test | inspection apparatus used for a test | inspection of a modulator. It is a flowchart of the inspection method of a modulator.

[Description of Embodiment of Present Invention]
First, the contents of the embodiments of the present invention will be listed and described.

The present invention includes (1) a waveguide formed on a substrate and defined by a side surface and an upper surface and having an end surface; and a resin that embeds the waveguide on the substrate, and the waveguide has a side surface and an upper surface. In the optical semiconductor element, the non-resin region in which the resin is not provided extends over a predetermined distance from the end surface in a direction in which the waveguide extends.
(2) The waveguide constitutes a Mach-Zehnder modulator including an input waveguide, an optical branching unit, two arms, an optical multiplexing unit, and an output waveguide, and the non-resin region includes the input resin You may extend from the end face of the waveguide to the optical branching section or halfway.
(3) The non-resin region may extend from the end face of the output waveguide to the optical multiplexing part or halfway.
(4) The resin may be benzocyclobutene.
According to another aspect of the present invention, (5) a waveguide defined by a side surface and an upper surface and having an end surface is formed on a substrate, the waveguide is embedded on the substrate with a resin, and the waveguide extends from the end surface. The method of manufacturing an optical semiconductor device, wherein the resin is removed over a predetermined distance.
Another invention of the present application includes (6) a semiconductor waveguide formed on a substrate, defined by a side surface and an upper surface, and having an end surface, and a resin that embeds the waveguide on the substrate, A method of inspecting an optical semiconductor device in which a non-resin region in which the resin is not provided on a side surface and an upper surface extends from the end surface in a direction in which the waveguide extends over a predetermined distance, and the waveguide is made by causing light to enter the end surface. This is an optical semiconductor device inspection method for measuring an electrical signal obtained from the above.
(7) Light may be incident on the end face from an optical fiber, and the position of the optical fiber may be determined according to the measurement result of the electrical signal.
(8) Light may be incident on the end face from an optical fiber via a lens, and the positions of the optical fiber and the lens may be determined according to the measurement result of the electrical signal.

[Details of the embodiment of the present invention]
Specific examples of an optical semiconductor device, an optical semiconductor device manufacturing method, and an optical semiconductor device inspection method according to an embodiment of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

  First, prior to the description of the embodiment, an outline of the modulator 200 according to the comparative example will be described. FIG. 1 is a perspective view of an optical waveguide portion of the modulator 200. As illustrated in FIG. 1, the modulator 200 has a configuration in which a Mach-Zehnder modulator 1 configured by combining paths of mesa-shaped optical waveguides is provided on a substrate 10. The Mach-Zehnder modulator 1 includes two input waveguides 21a and 21b, an optical coupler 22 that is connected to the input waveguides 21a and 21b, and branches the light input from the input waveguide 21a. Two modulated waveguides (arms) 23a and 23b for propagating the transmitted light, an optical coupler 24 for multiplexing the light propagated through the modulated waveguides 23a and 23b, and output light from the optical coupler 24 to the outside And guiding output waveguides 25a and 25b.

  In the example of FIG. 1, 2 × 2 couplers are used as the optical couplers 22 and 24. In FIG. 1, a ground electrode 32 described later is shown. Although the semiconductor may not be formed in a region other than the mesa-shaped optical waveguide, the semiconductor layer 50 is formed in a region other than the ground electrode 32 in FIG.

  FIG. 2 is a perspective view including a resin covering the optical waveguide portion. In FIG. 2, the path of the optical waveguide forming the Mach-Zehnder modulator 1 is indicated by a dotted line. As illustrated in FIG. 2, in the modulator 200, the resin 40 covers the Mach-Zehnder modulator 1. Thereby, the mesa forming the optical waveguide is embedded by the resin 40. The resin 40 is an organic material such as BCB (benzocyclobutene).

  The wiring pattern includes p-side traveling-wave electrodes 31a and 31b, an n-side ground electrode 32, and p-side phase adjustment electrodes 33a and 33b. The ground electrode 32 is provided in the opening of the resin 40 formed between the modulation waveguide 23a and the modulation waveguide 23b. Wiring patterns other than the ground electrode 32 are provided on the resin 40. Wiring patterns other than the ground electrode 32 are connected to the Mach-Zehnder modulator 1 through an opening formed in the resin 40.

  The traveling wave type electrode 31a is connected to the modulation waveguide 23a of FIG. The traveling wave electrode 31b is connected to the modulation waveguide 23b of FIG. When a high-frequency electrical signal is supplied to the traveling wave electrodes 31 a and 31 b, a high-frequency electrical signal flows between the ground electrode 32. As a result, the refractive indexes of the modulation waveguides 23a and 23b change, and the phase of light passing through the modulation waveguides 23a and 23b changes. Thereby, the light output from the output waveguides 25a and 25b is turned on / off, and a modulation signal is obtained.

  On the modulation waveguide 23a of FIG. 1, a phase adjustment electrode 33a is connected to be separated from the traveling wave electrode 31a. On the modulation waveguide 23b of FIG. 1, a phase adjustment electrode 33b is connected to be separated from the traveling wave type electrode 31b. A DC signal is supplied from the outside to the modulation waveguide 23a from the phase adjustment electrode 33a. Thereby, the phase of the light propagating through the modulation waveguide 23a is adjusted. A DC signal is supplied from the outside to the modulation waveguide 23b from the phase adjustment electrode 33b. Thereby, the phase of the light propagating through the modulation waveguide 23b is adjusted.

  When the modulator 200 is used, laser light having a high light intensity is incident on the input waveguide 21a from the outside as input light. If the input light deviates from the input waveguide 21a and is condensed on the resin 40, the resin 40 is decomposed and vaporized by the high energy of the laser light, and there is a possibility that a failure to reattach to the end face may occur. In particular, since the width of the optical waveguide of the modulator is as narrow as about several μm (for example, 1.5 μm), the input light tends to easily enter the resin. The reattached resin causes light absorption and scattering. As a result, optical loss may increase, leading to a decrease in incidence efficiency.

  Therefore, in the following embodiments, an optical semiconductor element capable of suppressing decomposition and vaporization of resin, a method for manufacturing the optical semiconductor element, and an inspection method for the optical semiconductor element will be described.

(Embodiment)
FIG. 3 is a perspective view of the modulator 100 according to the embodiment, and corresponds to FIG. Hereinafter, differences from the modulator 200 of FIGS. 1 and 2 will be described. In addition, about the same structure as the modulator 200, description is abbreviate | omitted by attaching | subjecting the same code | symbol. As illustrated in FIG. 3, the modulator 100 is different from the modulator 200 in that the resin 40 is not provided around the end face of the input waveguide 21a. With this configuration, the side surface and the upper surface of the input waveguide 21a are exposed around the end surface of the input waveguide 21a defined by the side surface and the upper surface.

  FIG. 4A is an end view of the input waveguide 21a. As illustrated in FIG. 4A, the resin 40 is not provided over a predetermined width around the input waveguide 21a on the end face of the input waveguide 21a. In addition, the width | variety of the area | region (henceforth non-resin area | region) in which the resin 40 is not provided is not specifically limited. For example, the non-resin region may be a region from one side end surface of the modulator 100 to the other side end surface. Further, the non-resin region may be a region from the input waveguide 21a to the middle of the side end surface on the side close to the input waveguide 21a. Further, the non-resin region may be a region from the input waveguide 21a to the input waveguide 21b or in the middle thereof. For example, the non-resin region preferably has a width of 10 μm or more on both sides with the input waveguide 21a as the center. More preferably, both sides have a width of 25 μm or more. Note that the width of the non-resin region may be equal to or greater than the focus error with respect to the end face of the input waveguide 21a from the external device.

  FIG. 4B is a top view of the periphery of the input waveguide 21a. As illustrated in FIG. 4B, a non-resin region is provided over a predetermined distance from the end face of the input waveguide 21a in the depth direction (the direction in which the input waveguide 21a extends). In addition, the depth distance of a non-resin area | region is not specifically limited. For example, the non-resin region may be a region from the end face of the input waveguide 21a to the optical coupler 22 or in the middle thereof. For example, the non-resin region preferably has a depth distance of 20 μm or more from the end face of the input waveguide 21a, and more preferably has a depth distance of 50 μm or more. Note that the depth distance of the non-resin region may be equal to or greater than the focus error with respect to the end face of the input waveguide 21a from the external device.

  According to this embodiment, the resin 40 is not provided around the end face of the input waveguide 21a. In this case, the light input to the input waveguide 21a is prevented from being focused on the resin 40, and decomposition / vaporization of the resin 40 is suppressed. This suppresses the resin from reattaching to the end face of the input waveguide 21a. As a result, light absorption and light scattering are suppressed, and a decrease in incident efficiency is suppressed.

(Modification)
FIG. 5 is a perspective view of a modulator 100a according to a modification. The difference between the modulator 100a and the modulator 100 is that the resin 40 is not provided around the end face of the output waveguide 25a. Thereby, the side surface and the upper surface of the output waveguide 25a are exposed around the end surface of the output waveguide 25a defined by the side surface and the upper surface. In such a configuration, the decomposition / vaporization of the resin 40 can be suppressed when the modulator 100 is inspected while light is incident on the output waveguide 25a. The non-resin region around the end face of the output waveguide 25a may have the same shape as the non-resin region around the end face of the input waveguide 21a. Further, the non-resin region may be provided around the end face of the output waveguide 25b.

(Production method)
Next, a method for manufacturing the modulator 100 will be described. FIG. 6A to FIG. 6F are manufacturing flow diagrams in the vicinity of one of the optical waveguides taken along the lines AA and BB in FIG. First, as illustrated in FIG. 6A, an n-type InP lower cladding layer 51, an AlGaInAs well layer, and an AlInAs barrier layer are formed on an n-type InP substrate 10 by metal organic vapor phase epitaxy (MOVPE). Crystal growth including the MQW-containing core layer 52, the p-type InP upper cladding layer 53, and the p + -type InGaAs contact layer 54 is performed.

Next, as illustrated in FIG. 6B, an SiO ₂ film 55 is formed on the wafer obtained in the growth step of FIG. 6A by using, for example, a thermal CVD method, and the lithography method is used. Then, the SiO ₂ film 55 is patterned into the shape of an optical waveguide. Next, as illustrated in FIG. 6C, the lower cladding layer 51, the core layer 52, the upper cladding layer 53, and the contact layer are formed by chlorine-based reactive ion etching (RIE) using the SiO ₂ film 55 as a mask. 54 is processed and a mesa is formed. For example, the optical waveguide width is 1.5 μm and the mesa height is 3 μm.

Next, as illustrated in FIG. 6D, the SiO ₂ film 55 is removed by wet etching using buffered hydrofluoric acid. Next, as illustrated in FIG. 6E, a new SiO ₂ film 56 for protecting the semiconductor surface is formed by a thermal CVD method. Next, as illustrated in FIG. 6 (f), the resin 40 is spin-coated to a thickness of 6 μm to flatten the surface, and is cured by curing at a high temperature of about 300 ° C.

  FIGS. 7A to 7F and FIGS. 8A to 8D are manufacturing flow diagrams after FIG. 6F. FIGS. 7A to 7C and FIGS. 8A to 8B correspond to the periphery of the modulation waveguide 23a on the AA line cross section of FIG. FIGS. 7D to 7F and FIGS. 8C to 8D correspond to the periphery of the input waveguide 21a on the BB line cross section of FIG. In addition, the manufacturing process in the location in which the traveling wave type electrode 31b and the phase adjustment electrodes 33a and 33b are provided is common to the cross section taken along the line BB.

As illustrated in FIG. 7A, the resin 40 is etched by, for example, RIE using a mixed gas of CF ₄ and O ₂ . Thereby, the SiO ₂ film 56 on the upper surface of the modulation waveguide 23a is exposed. The opening width of the resin 40 is, for example, about 10 μm. Note that, as illustrated in FIG. 7D, in the cross section taken along the line BB, etching is not performed by forming a mask or the like.

Next, as illustrated in FIG. 7B, the SiO ₂ film 56 on the modulation waveguide 23a is removed by fluorine RIE or the like. Note that, as illustrated in FIG. 7E, in the cross section taken along the line BB, etching is not performed by forming a mask or the like. Next, as illustrated in FIGS. 7C and 7F, a Ti / Pt / Au ohmic electrode 57 is deposited over the entire surface of the wafer and lifted off.

Next, as illustrated in FIGS. 8A and 8C, the traveling wave electrode 31a having a thickness of 3 μm, for example, is formed by performing Au plating on the ohmic electrode 57 on the modulation waveguide 23a. To do. The ohmic electrode 57 in a region other than the traveling wave electrode 31a is removed by milling or the like. Next, as illustrated in FIG. 8D, the resin 40 in the vicinity of the end face of the input waveguide 21a on the light input side is removed by RIE using a mixed gas of CF ₄ and O ₂ . Note that, as illustrated in FIG. 8B, etching is not performed using a mask or the like in a region other than the vicinity of the end face of the input waveguide 21a. Thereafter, the modulator 100 of FIG. 3 is obtained through a back surface process and a chip cleaving process.

  The optical waveguide provided with the traveling wave electrode 31b and the phase adjustment electrodes 33a and 33b modulation waveguide 23b is shown in FIGS. 6 (a) to 6 (f), FIGS. 7 (a) to 7 (c), and It can be formed by a process similar to that shown in FIGS. In the modulator 100a according to the modified example, the same processes as in FIGS. 6A to 6F, FIGS. 7D to 7F, and FIGS. 8C to 8D are performed. The non-resin region of the output waveguide 25a can be formed.

(Inspection method)
Next, a method for inspecting the modulator will be described. As an example, an inspection method of the modulator 100a according to the modification will be described. FIG. 9 is a schematic diagram of an inspection apparatus 300 used for inspection of the modulator 100a. As illustrated in FIG. 9, the traveling wave electrodes 31a and 31b and the ground electrode 32 are connected to the voltage / ammeter 61 by wiring. Further, the optical fiber 63 is optically coupled to the input waveguide 21a using a plurality of lenses 62. The output waveguide 25 a is optically coupled to the optical fiber 65 using a plurality of lenses 64. The plurality of lenses 62, the optical fiber 63, the plurality of lenses 64, and the optical fiber 65 are each held by a rod having a fine movement mechanism, and each moves within a range of about ± 20 μm with an accuracy of about ± 1 μm. Can do.

  FIG. 10 is a flowchart of an inspection method for the modulator 100a. Hereinafter, an inspection method of the modulator 100a will be described with reference to FIGS. First, using a voltmeter / ammeter 61 between the p-side traveling wave electrodes 31a and 31b and the n-side ground electrode 32, for example, a current is measured while applying a reverse bias voltage of −3 V, for example ( Step S1). In a state where no light is incident on the input waveguide 21a, almost no current flows.

  Next, it is considered that light enters the input waveguide 21a while the plurality of lenses 62 and the optical fiber 63 are brought close to the input waveguide 21a and the plurality of lenses 62, the optical fiber 63, and the modulator 100a are observed with a microscope. Arrange at the position (step S2). At this time, the input waveguide 21a and the focal positions of the plurality of lenses 62 include a deviation of about ± 10 μm.

  Next, inspection light is incident on the optical fiber 63 (step S3). For example, the wavelength is 1.55 μm, and the light intensity is 0 dBm to +17 dBm (for example, +13 dBm). If the light intensity exceeds 10 dBm and the resin is located at the light condensing point, there is a concern about resin vaporization. When light enters the input waveguide 21a, a current caused by photocarriers flows between the traveling wave electrodes 31a and 31b and the ground electrode 32. Therefore, while measuring the current using the voltmeter / ammeter 61, the positions of the plurality of lenses 62 and the optical fiber 63 are moved in the three directions xyz illustrated in FIG. And the position of the optical fiber 63 is searched (step S4). At the position where the current is maximized, the plurality of lenses 62 and the optical fiber 63 are fixed, and the inspection light is stopped (step S5). When the current is maximum, the optical coupling between the plurality of lenses 62 and the optical fiber 63 and the input waveguide 21a is the best.

  The focal lengths of the plurality of lenses 62 used here are 2 mm to 3 mm (for example, 2 mm). The numerical aperture NA of the lens is about 0.2 to 1 (for example, 0.5). The spot diameter condensed on the end face of the modulator 100a is 2 μm to 6 μm (for example, 3 μm). Since high-intensity light of about +13 dBm is focused on the 3 μm spot diameter region, the condensed region becomes high temperature. At the time when the light is incident, there is a possibility that the condensing point is shifted by about ± 10 μm from the position of the input waveguide 21a. However, since the resin 40 in this range is removed in the modulator 100a, the resin 40 The condensing point is not located.

  Next, the position of the plurality of lenses 64 and the optical fiber 65 is adjusted in the same way for the output waveguide 25a (step S6). That is, a plurality of lenses 64 and an optical fiber 65 are arranged in the vicinity of the output waveguide 25 a while observing with a microscope, and inspection light is incident from the optical fiber 65. Thereby, the inspection light is collected near the end face of the output waveguide 25a. While observing the current flowing between the traveling wave type electrodes 31a and 31b and the ground electrode 32 with the voltmeter / ammeter 61, the positions of the plurality of lenses 64 and the optical fiber 65 are finely adjusted, and the position where the current becomes maximum is determined. look for. The plurality of lenses 64 and the optical fiber 65 are fixed at the position where the current is maximum.

  Next, the optical fiber 63 is connected to the photodetector in a state where the inspection light is incident on the output waveguide 25a. While sweeping the voltage between the traveling wave electrodes 31a and 31b and the ground electrode 32 from 0V to -10V, the output intensity of light is measured by the photodetector (step S7). As a result, the voltage and the light output characteristic can be inspected. Through the above process, the inspection of the modulator 100a is completed. According to the inspection method, the modulator 100a can be inspected while suppressing the decomposition / vaporization of the resin 40. Even when the modulator 100 is inspected by the inspection method, the modulator 100 can be inspected while suppressing decomposition and vaporization of the resin 40 on the light input side.

  In the above example, an InP-based modulator using a high-mesa waveguide formed in a stripe shape from the upper surface to the core layer has been described as an example. However, other optical semiconductor elements having a light input waveguide (optical The above example can also be applied to a switch, a waveguide incident type light receiving element, an optical amplifier, an optical integrated element, and the like. The waveguide form may be a ridge waveguide formed in a stripe shape from the upper surface to the upper cladding layer.

1 modulator, 10 substrate, 21a, 21b input waveguide, 22 optical coupler, 23a, 23b modulation waveguide, 24 optical coupler, 25a, 25b output waveguide, 31a, 31b traveling wave electrode, 32 ground electrode, 33a, 33b Phase adjustment electrode, 40 resin, 50 semiconductor layer, 51 lower clad layer, 52 core layer, 53 upper clad layer, 54 contact layer, 55 SiO ₂ film, 56 SiO ₂ film, 57 ohmic electrode, 61 voltage / ammeter, 62 lens, 63 optical fiber, 64 lens, 65 optical fiber, 100 modulator, 200 modulator, 300 inspection device

Claims (7)

A waveguide formed on a substrate and defined by side and top surfaces and having an end surface;
Covering the side and top surfaces of the waveguide on the substrate, and embedding the waveguide; and
The waveguide constitutes a Mach-Zehnder modulator including an input waveguide, an optical branching unit, two arms, an optical multiplexing unit, and an output waveguide,
An optical semiconductor element, wherein a non-resin region in which the resin is not provided on a side surface and an upper surface of the waveguide extends for a predetermined distance from the end surface in a direction in which the waveguide extends. The optical semiconductor element according to claim 1, wherein the non-resin region extends from an end face of the input waveguide to the optical branching portion or partway.   The optical semiconductor element according to claim 2, wherein the non-resin region extends from an end face of the output waveguide to the optical multiplexing unit or partway.   The optical semiconductor element according to claim 1, wherein the resin is benzocyclobutene.   The optical semiconductor element according to claim 1, wherein the non-resin region is a region extending on both sides of the waveguide.   The resin has an opening on the waveguide;
  The optical semiconductor element according to claim 1, further comprising an electrode provided in the opening and connected to the waveguide. Forming on the substrate a waveguide defined by side and top surfaces and having end faces;
Embedding the waveguide with resin on the substrate,
Removing the resin over a predetermined distance from the end face in the extending direction of the waveguide ;
The waveguide constitutes a Mach-Zehnder modulator including an input waveguide, an optical branching unit, two arms, an optical multiplexing unit, and an output waveguide,
The method of manufacturing an optical semiconductor element , wherein the resin covers a side surface and an upper surface of the waveguide, and the resin is not provided on the side surface and the upper surface of the waveguide at the predetermined distance .

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