JP2009027088A - Semiconductor light-emitting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light-emitting device for protecting a VCSEL from high humidity and high temperature. <P>SOLUTION: A semiconductor light-emitting device 10 includes a VCSEL 20 for emitting light, a glass substrate 30 for transmitting the light emitted from the VCSEL 20, and a conductive silicon substrate 40, which has a recessed portion 40a in one side of the plane and houses the VCSEL 20 in the recessed portion 40a. On the surface of the silicon substrate 40, a p-side electrode layer 42 is formed via an insulating layer 46 so as to surround the recessed portion 40a, and on the backside of the silicon substrate layer 40, an n-side electrode layer 44 is formed. When the recessed portion 40a is covered by the glass substrate 30, the upper electrode 22 of the VCSEL 20 and the p-side electrode layer 42 are connected to a transparent electrode layer 32, formed on the backside of the glass substrate 30. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor light emitting device used as a light source for optical information processing or optical communication.

  In the technical fields such as optical communication and optical recording, interest in a light source of a surface-emitting semiconductor laser (Vertical-Cavity Surface-Emitting Laser: hereinafter referred to as VCSEL) is increasing. Since VCSELs are likely to deteriorate when exposed to moisture or moisture, they are usually sealed in cans or resins. Several techniques relating to sealing are disclosed in several patent documents.

  Patent document 1 is a semiconductor device provided with the liquid resin which coat | covers a semiconductor element, and the surface hardening layer formed by hardening | curing the surface of this liquid resin. The liquid resin protects the semiconductor element from the outside air and promotes heat dissipation of the semiconductor device.

  Patent Document 2 is an optical device that includes an optical element, a substrate, and a flexible substrate that covers the optical element mounted on the substrate. By utilizing the flexible base material, the optical element connected to the substrate is sealed to prevent deterioration of the optical element.

  Patent Document 3 is an optical module having an optical element, a substrate, and a package having moisture resistance. By utilizing the package, the optical element connected to the substrate is sealed to prevent the optical element from deteriorating.

JP-A-7-335982 JP 2002-151705 A JP-A-2005-353637

  Semiconductor light emitting devices such as VCSELs and LEDs may be required to operate stably under high temperature and high humidity conditions. If the semiconductor light emitting element is sealed with ceramic or can, moisture and moisture from the outside can be prevented and heat can be effectively dissipated. However, there is a problem that the cost of the sealing is high. On the other hand, when the semiconductor light emitting element is sealed with resin, moisture or moisture may enter from the interface between the external terminal and the resin, and the semiconductor light emitting element may be deteriorated. Further, in the case of resin sealing, the heat dissipation characteristics are not so good, and in particular, in the case of a device having temperature characteristics such as a VCSEL, the output greatly decreases as the temperature rises.

  An object of the present invention is to provide a semiconductor light emitting device capable of effectively protecting a semiconductor light emitting element from external moisture and temperature.

  A semiconductor light-emitting device according to the present invention includes a semiconductor light-emitting element that includes an upper electrode and a back electrode and emits light, a sealing substrate in which a first conductive layer is formed on one main surface, and one main surface And a conductive substrate having a second conductive layer formed on one main surface through an insulating layer so as to surround at least the recess, and the semiconductor light emitting element is disposed in the recess. The back electrode of the semiconductor light emitting element is electrically connected to the substrate in the recess, and the sealing substrate is attached on one main surface of the substrate so as to cover the recess, The upper electrode of the light emitting element and the second conductive layer of the substrate are electrically connected to the first conductive layer of the sealing substrate.

  Preferably, a third conductive layer is formed on the other main surface opposite to one main surface of the substrate, and the third conductive layer is electrically connected to the back electrode of the semiconductor light emitting element through the substrate. Connected. Preferably, a fourth conductive layer connected to the back electrode of the semiconductor light emitting element is formed in the recess. The fourth conductive layer may include a plurality of bump electrodes.

  The sealing substrate and the first conductive layer may transmit light emitted from the semiconductor light emitting element, and the substrate, the third conductive layer, and the fourth conductive layer may be the semiconductor light emitting element. The outgoing light may be transmitted.

  Preferably, the substrate is a silicon substrate doped with impurities, and the recess is formed on one main surface of the silicon substrate. Alternatively, the substrate may include a silicon substrate having a flat main surface and an insulating member attached on the silicon substrate and provided on the main surface of the silicon substrate so as to form the recess. Good.

  The semiconductor light emitting element is, for example, an LED or a VCSEL. The semiconductor light emitting device can include a light receiving element that receives part of the light emitted from the semiconductor light emitting element in the recess, and can further include a drive circuit element that drives the semiconductor light emitting element in the recess.

  According to the present invention, the semiconductor light emitting element can be protected from external moisture or the like by housing the semiconductor light emitting element in the recess of the substrate. Further, by attaching the semiconductor light emitting element on a conductive substrate having good thermal conductivity such as a silicon substrate, the semiconductor light emitting element can be efficiently radiated.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1A is a perspective view of a semiconductor light emitting device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA of FIG. The semiconductor light emitting device 10 includes a VCSEL 20 that emits laser light, a glass substrate 30 that transmits light emitted from the VCSEL 20, and a silicon substrate in which a rectangular recess is formed on one surface and the VCSEL 20 is accommodated in the recess. 40. In the drawing, an arrow S indicates how the laser light emitted from the VCSEL 20 passes through the glass substrate 30.

  The VCSEL 20 is, for example, a chip having a side of about several 50 to 100 μm, and is smaller and thinner than the conventional one. The p-side upper electrode 22 is formed on the upper surface of the VCSEL 20, and the n-side back electrode 24 is formed on the rear surface. By applying a forward current to the upper electrode 22 and the back electrode 24, the VCSEL 20 A laser beam is emitted.

  The glass substrate 30 is a rectangular flat plate that covers the recess 40 a of the silicon substrate 40. A transparent electrode layer 32 is formed on the entire back surface of the glass substrate 30 by sputtering or the like. The transparent electrode layer 32 is, for example, a conductive thin film such as ITO and transmits the laser light of the VCSEL 20. The transparent electrode 32 is connected to the upper electrode 22 of the VCSEL 20 and to a p-side electrode layer 42 formed so as to surround the recess 40 a of the silicon substrate 40.

  The silicon substrate 40 is a rectangular parallelepiped having a side of about 300 to 500 μm, and a concave portion 40a capable of accommodating the VCSEL 20 is formed on one surface. The recess 40a is preferably formed by anisotropically etching the silicon substrate using a resist pattern formed by a known photolithography process as a mask. The silicon substrate 40 has n-type conductivity, for example, by doping impurities such as arsenic and phosphorus. The silicon substrate 40 itself functions as a current path, and it is desirable that the silicon substrate 40 be doped at a relatively high concentration in order to form the n-side electrode layer 44 on the back surface as will be described later.

  An insulating film 46 such as a silicon oxide film is preferably formed on the surface of the silicon substrate 40. The p-side electrode layer 42 is formed on the insulating film 46 so as to surround the recess 40a. The p-side electrode layer 42 is electrically insulated from the silicon substrate 40 by the insulating film 46. A part of the p-side electrode layer 42 further extends to a position exposed by the glass substrate 30 on the silicon substrate 40, and an electrode pad 42a is formed there. An n-side electrode layer 44 that is in ohmic contact with the silicon substrate 40 is formed on the entire back surface of the silicon substrate 40. The p-side electrode layer 42 and the n-side electrode layer 44 are made of, for example, Au.

  Bump electrodes 48 are formed on the bottom surface of the recess 40a of the silicon substrate 40. The bump electrode 48 is connected to the back electrode 24 of the VCSEL 20 accommodated in the recess 40a. The bump electrode 48 may be a film formed at a uniform height on the entire surface of the recess 40a, or may be a plurality of electrodes in the form of balls or protrusions.

  FIG. 2A is a cross-sectional view showing a typical configuration of the VCSEL 20. The VCSEL 20 includes an n-side back electrode 24 on the back surface of an n-type GaAs substrate 210, and a lower DBR (Distributed Bragg Reflector: distribution) composed of an n-type GaAs buffer layer 224 and an n-type AlGaAs semiconductor multilayer film on the substrate 210. Bragg reflector 226, active region 228, current confinement layer 230 including a region where the outer edge of p-type AlAs is oxidized, upper DBR 232 made of a p-type AlGaAs semiconductor multilayer film, and p-type GaAs contact layer 234 It is out.

  The substrate 210 is formed with a ring-shaped groove 236 having a depth that reaches a part of the lower DBR 226 from the contact layer 234, and the groove 236 allows the cylindrical post P, which is a laser light emitting portion, and the bonding region 238 to be formed. Is stipulated. A p-side upper electrode 22 a that is ohmically connected to the contact layer 234 through a contact hole in the interlayer insulating film 240 is formed on the top of the post P. In the center of the upper electrode 22a, a circular emission port 244 that defines a laser beam emission region is formed. In the junction region 238, an electrode layer 22b is formed via an interlayer insulating film 240, and the electrode layer 22b is connected to the upper electrode 22a. The upper electrode 22 a and the electrode layer 22 b can constitute the upper electrode 22 of the VCSEL 20, and the upper electrode 22 a and the electrode layer 22 b can be connected to the transparent electrode layer 32 of the glass substrate 30.

  FIG. 2B is a cross-sectional view showing a configuration example of another VCSEL. As shown in the figure, in the bonding region 238, the upper electrode 22c is further formed on the upper electrode 22b, so that it is higher than the upper electrode 22a of the post P. As a result, only the upper electrode 22c can be connected to the transparent electrode 32, the upper electrode 22a of the post P can be free, and no load can be applied to the post P.

The VCSEL 20 is driven as follows. A forward bias voltage is applied to the p-side electrode layer 42 and the n-side electrode layer 44 of the silicon substrate 40. The p-side electrode layer 42 is electrically connected to the upper electrode 22 of the VCSEL 20 via the transparent electrode 32 of the glass substrate 30, and the n-side electrode layer 44 is connected to the back electrode 24 via the silicon substrate 40 and the bump electrode 48. Electrically connected. When a current exceeding the threshold value is applied to the VCSEL 20, laser light is emitted from the center of the post P, that is, the emission port 244 of the upper electrode 22a. The wavelength of the laser light is, for example, 850 nm.
The emitted laser light passes through the transparent electrode 22 and the glass substrate 30 and is output to the outside.

  According to the semiconductor light emitting device 10 of the present embodiment, the VCSEL 20 is accommodated in a sealed space in the silicon substrate, so that it is not exposed to the outside air, and deterioration due to humidity can be prevented. The heat in the VCSEL 20 or the recess 40a can be effectively radiated to the outside through the silicon substrate 40 and the metal electrode layer having high thermal conductivity. Furthermore, by enabling mounting on a silicon substrate, the size of the VCSEL chip can be reduced, so that a large number of VCSEL chips can be taken from one wafer, and the manufacturing cost can be reduced. In addition, the heat dissipation characteristics are further improved by thinning the VCSEL chip. Further, since the semiconductor light emitting device 10 has the p-side electrode layer 42 and the n-side electrode layer 44 on the top surface and the back surface, respectively, similarly to the VCSEL 20, it can be packaged using the same mounting method as the conventional one. is there.

  Next, a method for manufacturing a semiconductor light emitting device according to an embodiment of the present invention will be described with reference to FIG. First, the VCSEL 20 is bonded to the glass substrate 30 as shown in FIG. Preferably, the upper electrode 22 of the VCSEL 20 and the transparent electrode layer 32 are joined by heat treatment. At this time, a conductive thin film having a low melting point, such as an indium thin film, may be formed on the upper surface of the upper electrode 22 and bonded at a low temperature by ITO / In / Au. The bonding method is not limited to this, and a resin containing conductive particles may be interposed between the upper electrode 22 b and the transparent electrode 32. In this case, the upper electrode 22a of the post P of the VCSEL 20 is separated from the transparent electrode 32, and the load on the post P can be eliminated.

  Next, as shown in FIG. 3B, the VCSEL 20 is accommodated in the recess 40 a of the silicon substrate 40, the back electrode 24 of the VCSEL 20 is connected to the bump electrode 48, and the p-side electrode layer 42 is connected to the transparent electrode 32. Is done. This joining process is performed by performing a heat treatment or the like at a constant temperature as described above. Thereby, the p electrode layer 42 formed on the surface of the silicon substrate 40 is electrically connected to the upper electrode 22 of the VCSEL 20 through the transparent electrode layer 32. At the same time, the n-side electrode layer 44 is electrically connected to the back electrode 24 of the VCSEL element 20 via the pump electrode 48.

  Next, another embodiment of the present invention will be described. In the above-described embodiment, an example in which the concave portion is formed on the surface of a single silicon substrate has been described. However, the present invention is not limited to this. For example, as shown in FIG. An insulating member 62 for forming the recess 60 a may be formed on the substrate 60. A p-side electrode layer 64 for connecting to the transparent electrode 32 of the glass substrate 30 is formed on the surface of the insulating member 62. An n-side metal layer 66 is formed on the back surface of the silicon substrate 60. As the insulating member 62, for example, a ceramic member or other insulating resin can be used.

  Further, the glass substrate 30 covering the concave portion is not necessarily a parallel plate, and for example, as shown in FIG. 5, a glass substrate 70 having a convex surface may be used. Thereby, the light from VCSEL and other light emitting elements can be made to converge more. Further, in addition to the glass substrate, a substrate made of a material that is transmissive to light from the VCSEL 20 and other light-emitting elements can be used. For example, transparent polyimide may be used. Furthermore, in the said Example, although the silicon substrate was utilized, not only this but the other electroconductive board | substrate which has heat dissipation may be sufficient.

  In the above embodiment, the VCSEL laser beam is emitted from the glass substrate side. However, the present invention is not limited to this, and the VCSEL laser beam may be emitted from the opposite substrate. For example, when the wavelength of the laser light of the VCSEL is 1300 nm, a gallium arsenide (GaAs) substrate may be used as the substrate that transmits the emitted light.

  In the above embodiment, an example of a single spot where the VCSEL 20 emits laser light from a single post P has been shown, but a multi-spot where a plurality of posts are arranged and laser light is emitted therefrom may be used.

  Further, the semiconductor light emitting device may include a VCSEL driving circuit and a light receiving element for monitoring the output of the VCSEL. For example, the recess of the silicon substrate may include a VCSEL, a drive circuit that drives the VCSEL, and a light receiving element. Part of the laser light emitted by the VCSEL is reflected by the glass substrate 30 and received by the light receiving element, the detection signal is supplied to the drive circuit, and the drive circuit controls the drive so that the output of the VCSEL is constant. To do. In this case, since it is necessary to prepare the drive circuit and the p-side electrode layer of the light receiving element separately from the VCSEL, for example, a laminated substrate 80 having a multilayer wiring structure as shown in FIG. 6 is attached on the silicon substrate 60. You may do it. In the case of a multi-spot VCSEL, light receiving elements corresponding to the number of spots are arranged.

  The above-described embodiments are illustrative, and the scope of the present invention should not be construed as being limited thereto, and can be realized by other methods within the scope satisfying the constituent requirements of the present invention. Needless to say.

  Next, an example of an optical module to which the semiconductor light emitting device of this embodiment is applied will be described. In the optical module or package 300 shown in FIG. 7, the die pad 320 on which the semiconductor light emitting device 10 is mounted is fixed on a disk-shaped metal stem 330. The conductive leads 340 and 342 are inserted into through holes (not shown) formed in the stem 330. The lead 340 is electrically connected to the n-side electrode layer 44 of the semiconductor light emitting device 10 via the die pad 320, and the lead 342 is electrically connected to the p-side electrode layer 42 of the semiconductor light emitting device 10 by a bonding wire or the like. The

  A rectangular hollow cap 350 is fixed on the stem 330, and a ball lens 360 is fixed in the central opening of the cap 350. The optical axis of the ball lens 360 is positioned so as to coincide with the center of the light emitting optical axis of the semiconductor light emitting device 10. When a forward voltage is applied between the leads 340 and 342, the laser light is emitted from the VCSEL 20 and adjusted so that the ball lens 360 is included in the radiation angle θ. A light receiving element for monitoring the light emission state of the VCSEL 20 may be included in the cap.

  FIG. 8 is a diagram showing an example of another optical module, which is preferably used in a spatial transmission system described later. In the optical module 302 shown in the figure, a flat glass 362 is fixed in the central opening of the cap 350 instead of using the ball lens 360. The distance between the semiconductor light emitting device 10 and the flat glass 362 is adjusted so that the opening diameter of the flat glass 362 is not less than the radiation angle θ of the laser light from the semiconductor light emitting device 10.

  FIG. 9 is a cross-sectional view showing a configuration when the optical module shown in FIG. 7 is applied to an optical transmitter. The optical transmission device 400 includes a cylindrical casing 410 fixed to the stem 330, a sleeve 420 integrally formed on the end surface of the casing 410, a ferrule 430 held in the opening 422 of the sleeve 420, and a ferrule 430. The optical fiber 440 to be held is included. An end of the housing 410 is fixed to a flange 332 formed in the circumferential direction of the stem 330. The ferrule 430 is accurately positioned in the opening 422 of the sleeve 420 and the optical axis of the optical fiber 440 is aligned with the optical axis of the ball lens 360. The core wire of the optical fiber 440 is held in the through hole 432 of the ferrule 430.

  Laser light from the VCSEL is collected by the ball lens 360, and the collected light is incident on the core of the optical fiber 440 and transmitted. Although the ball lens 360 is used in the above example, other lenses such as a biconvex lens and a plano-convex lens can be used.

  FIG. 10 is a diagram showing a configuration when the package shown in FIG. 7 is used in a spatial transmission system. The spatial transmission system 500 includes a package 300, a condenser lens 510, a diffusion plate 520, and a reflection mirror 530. The light condensed by the condenser lens 510 is reflected by the diffusion plate 520 through the opening 532 of the reflection mirror 530, and the reflected light is reflected toward the reflection mirror 530. The reflection mirror 530 reflects the reflected light in a predetermined direction and performs optical transmission.

  FIG. 11 is a diagram illustrating a configuration example of an optical transmission system using a semiconductor light emitting device as a light source. The optical transmission system 600 includes a light source 610 including the semiconductor light emitting device 10, an optical system 620 that collects laser light emitted from the light source 610, and a light receiving unit 630 that receives the laser light output from the optical system 620. And a control unit 640 that controls driving of the light source 610. The control unit 640 supplies a drive pulse signal for driving the semiconductor light emitting device 10 to the light source 610. Light emitted from the light source 610 is transmitted to the light receiving unit 630 via an optical system 620 by an optical fiber, a reflection mirror for spatial transmission, or the like. The light receiving unit 630 detects the received light with a photodetector or the like. The light receiving unit 630 can control the operation of the control unit 640 (for example, the start timing of optical transmission) by the control signal 650.

  Next, the configuration of an optical transmission device used in the optical transmission system will be described. FIG. 12 is a diagram illustrating an external configuration of the optical transmission apparatus. The optical transmission device 700 includes a case 710, an optical signal transmission / reception connector joint 720, a light emitting / receiving element 730, an electric signal cable joint 740, a power input unit 750, an LED 760 indicating that an operation is in progress, an LED 770 indicating occurrence of an abnormality, and a DVI. A connector 780 is provided.

  A video transmission system using the optical transmission apparatus 700 is shown in FIG. In these figures, the video transmission system 800 uses the optical transmission device shown in FIG. 12 to transmit the video signal generated by the video signal generation device 810 to the image display device 820 such as a liquid crystal display. That is, the video transmission system 800 includes a video signal generation device 810, an image display device 820, a DVI electric cable 830, a transmission module 840, a reception module 850, a video signal transmission optical signal connector 860, an optical fiber 870, and a control signal electrical. A cable connector 880, a power adapter 890, and an electric cable 900 for DVI are included.

  The semiconductor light emitting device according to the present invention can be used as a light source used in various fields such as optical information processing and optical high-speed data communication.

1A is a perspective view of a semiconductor light emitting device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA of FIG. It is sectional drawing which shows the structure of VECSEL. It is a figure which shows the manufacturing process of the semiconductor light-emitting device based on the Example of this invention. It is a figure which shows the modification of the semiconductor light-emitting device based on a present Example. It is a figure which shows the modification of the semiconductor light-emitting device based on a present Example. It is a figure which shows the modification of the semiconductor light-emitting device based on a present Example. It is a schematic diagram which shows the structural example of the optical module which mounted the semiconductor light-emitting device. It is a schematic diagram which shows the structural example of the other optical module which mounted the semiconductor light-emitting device. It is sectional drawing which shows the structure of the optical transmitter using the optical module shown in FIG. It is a figure which shows the structure of a spatial light transmission system. It is a block diagram which shows the structure of an optical transmission system. It is a figure which shows the external appearance structure of an optical transmission apparatus. It is a figure which shows the video transmission system using the optical transmission apparatus of FIG.

10: Semiconductor light emitting device 20: VCSEL
22: upper electrode 24: back electrode 30: glass substrate 32: transparent electrode layer 40: silicon substrate 40a: recess 42: p-side electrode layer 44: n-side electrode layer 46: insulating layer 48: bump electrode

Claims (13)

A semiconductor light emitting element including an upper electrode and a back electrode, and emitting light;
A sealing substrate having a first conductive layer formed on one main surface;
A concave portion is formed on one main surface, and a conductive substrate having a second conductive layer formed on one main surface via an insulating layer so as to surround at least the concave portion,
The semiconductor light emitting element is housed in the recess, a back electrode of the semiconductor light emitting element is electrically connected to the substrate in the recess, and the sealing substrate covers one of the main substrates so as to cover the recess. A semiconductor light emitting device mounted on a surface, wherein the upper electrode of the semiconductor light emitting element and the second conductive layer of the substrate are electrically connected to the first conductive layer of the sealing substrate. A third conductive layer is formed on the other main surface opposite to one main surface of the substrate, and the third conductive layer is electrically connected to the back electrode of the semiconductor light emitting element through the substrate. The semiconductor light-emitting device according to claim 1. The semiconductor light-emitting device according to claim 1, wherein a fourth conductive layer connected to a back electrode of the semiconductor light-emitting element is formed in the recess. The semiconductor light emitting device according to claim 3, wherein the fourth conductive layer includes a plurality of bump electrodes. The semiconductor light-emitting device according to claim 1, wherein the sealing substrate and the first conductive layer transmit light emitted from the semiconductor light-emitting element. The semiconductor light-emitting device according to claim 1, wherein the substrate transmits light emitted from the semiconductor light-emitting element. 7. The semiconductor light emitting device according to claim 1, wherein the substrate is a silicon substrate doped with impurities. The semiconductor light emitting device according to claim 7, wherein the recess is formed on one main surface of the silicon substrate. 2. The substrate according to claim 1, comprising: a silicon substrate having a flat main surface; and an insulating member attached on the silicon substrate and provided on the main surface of the silicon substrate so as to form the recess. Semiconductor light emitting device. The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting element is a surface emitting semiconductor laser. 11. A module comprising the semiconductor light emitting device according to claim 1 and an optical member that receives light emitted from the semiconductor light emitting device. An optical space transmission device comprising: the module according to claim 11; and a transmission unit that spatially transmits light emitted from the module. An optical space transmission system comprising the module according to claim 11 and a transmission means for spatially transmitting light emitted from the module.

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