JP2009071140A - Surface emission type device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface emission type device in which pressure is hardly concentrated on a light emission portion when a surface emission type element is bonded to a substrate having a pattern. <P>SOLUTION: The surface emission type device is constituted by arranging the surface emission type element 1000 on the substrate 2000 having the wiring pattern on its surface, wherein a radiation-side electrode having a window for emitting light from a light emission portion of the surface emission type element is formed on a light radiation surface of the surface emission type element, and a substrate-side electrode 10 of the surface emission type device and the wiring pattern 13 of the substrate 2000 are electrically connected at a portion other than right below the light emission portion. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting diode (LED) which is a surface emitting device, a surface emitting semiconductor laser (VCSEL), a surface emitting array device in which they are arranged at high density, and a manufacturing method thereof.

  An LED array suitable for downsizing and high resolution is used as a light source of a printer using an electrophotographic method, and an LED array having a light emitting dot density of 600 DPI as described in Patent Document 1 is used as a prior art. Are known.

  FIG. 6 is a diagram showing an LED array described in Patent Document 1. As shown in FIG. The LED array 101 has a plurality of light emitting dots 102. The light emitting dot 102 includes an ohmic electrode 103 disposed at the center and the periphery of the light emitting surface, and a light extraction region 106 divided into two by the center electrode.

  However, if the light emitting dots are made smaller in order to make the LED array compatible with higher definition, the proportion covered by the surface electrode increases, the light extraction area becomes smaller, and the light emission efficiency decreases. In addition, there is a problem that the variation in the light output of the light emitting dots increases due to a slight positional shift of the ohmic electrode and a decrease in dimensional accuracy. Furthermore, the reduction in the contact area between the ohmic electrode and the semiconductor layer causes problems such as an increase in ohmic resistance and non-uniform diffusion of the injection current.

  On the other hand, as a prior art for avoiding the above-described problem, there is known a mode in which a surface emitting laser is formed on a substrate transparent to an emission wavelength as described in Patent Document 2 and light is extracted through the substrate. .

  FIG. 7 is a diagram showing a surface emitting laser device described in Patent Document 2. As shown in FIG.

  The surface emitting laser element 111 has a p-side electrode 115 on the p-type substrate 112 side that is transparent to the emission wavelength, and an n-side electrode 114 on the epitaxial growth layer side. The surface emitting laser element 111 is closely fixed to a heat sink 118 formed of a Si substrate having excellent thermal conductivity via a solder material 117 on the side where the n-side electrode 114 is disposed. Light generated in the active layer 113 is output to the outside from the opening 116.

  In addition, a surface emitting diode array having a configuration in which an LED as described in Patent Document 3 is bonded to a support substrate has been proposed.

  FIG. 8 is a diagram showing a surface emitting diode array described in Patent Document 3. As shown in FIG.

A surface emitting diode is formed by a semiconductor process after epitaxially forming a semiconductor multilayer structure including a light emitting layer on a semiconductor substrate via a separation layer. Next, the semiconductor substrate is bonded to another substrate 126 having a wiring pattern formed on the surface, and the semiconductor substrate is removed. An n-type metal electrode 125 is formed except for the semiconductor layer 121, the insulating layer 122, the p-type region 123, the metal electrode 124 also serving as a reflection mirror, and the light emission region. It is also possible to form a driver IC on another substrate 126 and directly bond it to the lead wiring 127.
JP-A-11-121802 JP 2003-318488 A JP 2005-123522 A

  However, in the prior arts of Documents 2 and 3, since the surface-emitting diode is connected to another substrate immediately below the light-emitting portion, when electrical connection is performed by direct bonding between metals, the bonding pressure Is applied in a concentrated manner directly on the light emitting portion, and this has an effect on the light emission characteristics.

  Accordingly, an object of the present invention is to provide a device in which the pressure at the time of joining an element and a substrate is less likely to concentrate on the light emitting part on the element side and a method for manufacturing the same in a surface emitting device.

In order to solve the above problems, a surface-emitting device according to the present invention includes:
A surface-emitting device constructed by providing a surface-emitting element on a substrate having a wiring pattern on the surface,
A radiation-side electrode having a window for emitting light from the light emitting portion of the surface-emitting element is formed on the light-emitting surface of the surface-emitting element, and the substrate-side electrode of the surface-emitting element The wiring pattern of the substrate is electrically connected at a portion other than directly below the light emitting portion.

  In the surface-emitting type device of the present invention, one electrode of the surface-emitting type device is connected to the wiring pattern of the substrate as a substrate-side electrode, and the connection portion of this electrode is a portion other than directly below the light-emitting portion. For this reason, in a joining process, since a joining pressure does not concentrate on a light emission part, the influence on the light emission characteristic of a surface emitting device is reduced.

  Further, in the surface emitting device of this configuration, a high output is expected because there is no electrode that shields light emission on the light emission side.

  Such a surface-emitting type device is suitably used as a printer head such as an LED printer.

  An embodiment of the present invention will be described.

  FIG. 1 is a schematic cross-sectional view of a surface emitting device of the present invention.

  The present invention is a surface-emitting device 3000 configured by providing a surface-emitting element 1000 on a substrate 2000 such as a silicon substrate 12 having a wiring pattern on the surface, and has the following characteristics.

  First, a radiation-side electrode 14 having a window for emitting light from the light emitting portion 1020 of the surface-emitting element is formed on the light-emitting surface 1010 of the surface-emitting element. The substrate-side electrode 10 of the surface-emitting element and the wiring pattern 13 of the substrate 2000 are electrically connected at a portion other than directly below the light emitting portion. Here, the area immediately below the light emitting portion is an area of 1099.

  Note that the light emitting unit 1020 and the substrate 2000 of the surface light emitting element 1000 are configured so that there is a portion that is in thermal contact with the light emitting unit 1020 but is not electrically connected. You can also. For example, as shown in FIG. 2, a light-emitting element and a substrate having a pattern are not electrically connected immediately below the light-emitting portion, but a thermally conductive pad is provided between the two so that thermal conduction can be performed. be able to.

  The electrical connection between the substrate-side electrode 10 of the surface-emitting element 1000 and the wiring pattern 13 of the silicon substrate 12 can be performed by direct metal-to-metal bonding (gold to gold).

  Here, a plurality of surface-emitting elements can be arranged in a row to constitute a surface-emitting diode array. In such a case, the substrate side electrode 10 of the surface emitting diode can be an individual electrode, and the light emission side electrode 14 can be a common electrode of a plurality of surface emitting diodes.

  The surface-emitting type element 1000 can also be configured by a surface-emitting laser (for example, a vertical cavity surface-emitting laser: VCSEL).

  Furthermore, it is possible to provide a display device that includes a surface-emitting device as a component, an LED printer head that includes a surface-emitting device as a component, and a printer equipped with this head.

  Hereinafter, the manufacturing method of the surface emitting device according to the present invention will be described.

  A method for manufacturing a surface-emitting device according to the present invention is a method for manufacturing a surface-emitting device in which a surface-emitting device is formed on a substrate having a wiring pattern on the surface, and includes the following (a) to (d) It has the process.

(A) A step of forming a plurality of semiconductor layers including a light emitting layer on a compound semiconductor substrate (b) A step of forming a surface light emitting device on the semiconductor layer (c) A substrate having a wiring pattern is bonded, and the surface light emission The step of electrically connecting the electrode on the side to which the mold device is joined to the wiring pattern at a portion other than directly under the light emitting portion (d) removing the compound semiconductor substrate and corresponding to the light emitting portion on the removed surface Step of Forming Light Emission Side Electrode with Window Opened at Position A specific embodiment using a surface light emitting diode as a surface light emitting element will be described with reference to the drawings.

  3 is a cross-sectional view for explaining a process of forming a semiconductor layer on a GaAs substrate, FIG. 4 is a cross-sectional view of a silicon substrate on which a wiring pattern is formed, and FIG. 5 is a GaAs substrate after bonding the silicon substrate. It is sectional drawing for demonstrating the process of removing.

  As shown in FIG. 3A, layers are formed on a compound semiconductor substrate 1 such as GaAs by MOCVD, which is a known technique.

  The following layers are stacked on the GaAs substrate 1.

Separation layer _{2, n-Al z Ga 1} -z As layer 3, the current confinement layer _{(n-Al x Ga 1-} x As layer) 4, an active layer _{(n-Al y Ga 1-} y As layer) 5, a current A confinement layer (p-Al _x Ga _1-x As layer) 6 and a p-Al _z Ga _1-z As layer 7 (y <z <x) are sequentially formed.

  The impurity concentration and thickness of the epitaxial growth depend on the device design, but a typical configuration is as follows.

n-AlAs layer 2: ~ 0.01 μm; ~ 10 ¹⁸ / cm ³
n-Al0.2Ga0.8As layer 3: ~ 0.5μm; ~ 10 ¹⁸ / cm ³
n-Al0.35Ga0.65As layer 4: ~ 0.5μm; ~ 10 ¹⁸ / cm ³
p-Al0.13Ga0.87As layer 5: ˜0.1 μm; ˜10 ¹⁷ / cm ³
p-Al0.35Ga0.65As layer 6: ˜0.5 μm; ˜10 ¹⁷ / cm ³
p-Al0.2Ga0.8As layer 7: ˜0.5 μm; ˜10 ¹⁷ / cm ³
Subsequently, a surface emitting diode is formed on the epitaxial layer by a semiconductor process which is a known technique. The electrode is formed up to one electrode of the surface emitting diode. At this time, a region for connection is provided at a position away from the light emitting portion of the surface emitting diode.

  As shown in FIG. 3B, after the light emitting portion 71 and the joining portion 72 are etched into a mesa shape, the insulating layer 8 is formed on the entire surface by sputtering film formation. Subsequently, as shown in FIG. 3C, a contact window 9 is formed in the insulating layer 8 by photolithography and dry etching, covers the contact window 9, and is also connected to the electrode for the junction. A pattern of one metal electrode 10 is formed. In this step, a groove 11 reaching the separation layer 2 is also formed.

  On the other hand, a silicon substrate 12 that is a substrate on which a metal wiring pattern 13 is formed is prepared separately (FIG. 4). In the wiring pattern 13, a connection region corresponding to a region (junction) for connecting the surface-emitting diode is formed, and the surface on the GaAs substrate 1 is placed on the silicon substrate 12 so that the two regions coincide with each other. A light emitting diode is bonded on a wafer scale (FIG. 5A). This bonding is performed by direct bonding of the gold electrode of the surface-emitting diode and the gold-to-gold of the gold wiring pattern.

  Bonding is performed by bringing one electrode 10 of the surface emitting diode and the wiring pattern 13 into direct contact and applying pressure and heat. However, since the bonding portion is not directly under the light emitting portion, concentration of pressure is avoided and surface light emission is achieved. The influence on the light emitting characteristics of the diode is reduced.

  Next, the GaAs substrate 1 is removed. A groove 11 reaching the isolation layer 2 partially formed on the surface of the surface-emitting diode is used. After joining with the silicon substrate 12, it is possible to separate the GaAs substrate 1 by selectively etching the separation layer by flowing an etching solution containing hydrofluoric acid into the groove 11 (FIG. 5B). .

  Alternatively, as a method for removing the GaAs substrate, it is possible to use the difference in etching rate between GaAs and the separation layer 2 to remove the GaAs substrate 1 by etching and stop the etching at the separation layer 2. Specifically, the separation layer 2 is made of AlAs, and the GaAs substrate 1 is etched away by GaAs selective etching using a mixed solution of ammonia and hydrogen peroxide, and then the separation layer is removed by etching with hydrochloric acid or the like.

  Subsequently, the other metal electrode 14 is formed on the radiation side where the window is opened immediately above the light emitting portion on the surface from which the GaAs substrate 1 has been removed in the above-described process, so that the surface emitting diodes of FIGS. The form of is completed.

  As described above, a surface emitting diode having one electrode 10 connected thereto is formed on the silicon substrate 12 on which the wiring pattern 13 is formed. One electrode 10 is called a substrate side electrode, and the other electrode 14 is called a light emission side electrode. The light emitting region 16 represents a region that emits light by current injection in the active layer 5. The substrate-side electrode 10 is electrically connected to the wiring pattern 13 at a portion other than directly below the light emitting portion. When electrical connection is performed by direct bonding between metals, the pressure at the time of bonding is not concentrated on the light emitting portion as described above.

  When the substrate side electrode 10 and the light emission side electrode 14 are energized, the light emitting region 16 emits light. The light traveling toward the light emission side is radiated to the outside from a light emission window 15 formed on the light emission side electrode 14. Since there is no electrode that shields light radiation, the light output can be greatly increased. On the other hand, the light directed toward the substrate is reflected by the substrate-side electrode 10 toward the light emission side, so that the light output is further increased.

  In an LED array in which surface-emitting diodes are arranged in rows, the substrate-side electrodes of the surface-emitting diodes are individual electrodes, and there are a plurality of radiation-side electrodes having windows for emitting light from the surface-emitting diodes. This is a common electrode common to the surface emitting diodes. In the LED array configuration, individual electrodes are connected to a wiring pattern on a silicon substrate. Therefore, if an IC or a shift register for driving LEDs is formed on a separate substrate, it can be connected together by bonding, so that wire bonding is unnecessary, and the number of wire bondings can be greatly reduced.

  As shown in FIG. 2, it is good also as a structure which contacts the silicon substrate 12 in the vicinity of a light emission part. With this structure, it is possible to efficiently release heat generated in the light emitting portion to the silicon substrate 12 and further improve the heat dissipation characteristics. That is, a portion immediately below the light emitting portion of the surface emitting diode is not electrically connected to the substrate on which the wiring pattern is formed, but is in thermal contact. For this contact, it is possible to use a paste having excellent thermal conductivity.

  In addition, an electrically separated metal thin film can be used for the contact portion.

  Since the silicon substrate has high thermal conductivity and the light emitting portion is close to the silicon substrate, the emission is high and the temperature characteristics of the surface-emitting diode are improved. In the configuration of FIG. 2, it is necessary to select a material that does not affect the light emitting portion due to stress at the time of bonding.

  In the present embodiment, a normal surface emitting diode has been described as an example, but by applying to a resonant resonant light emitting diode (RC-LED) having a DBR mirror inside, or a surface emitting semiconductor laser, Similar effects can be obtained.

  The present invention provides an LED array having a small light emission size and a high density array necessary for high definition of an LED printer. The light emission size is small and a high-density array is realized, and the number of wire bonding that is a cost factor in the mounting process to the LED scanner can be greatly reduced.

Schematic sectional view of a surface emitting device of the present invention Schematic sectional view of a surface emitting device having a thermal contact portion of the present invention Sectional drawing for demonstrating the process of forming a semiconductor layer on a GaAs substrate Cross-sectional view of a silicon substrate on which a wiring pattern is formed Sectional drawing for demonstrating the process of removing a GaAs substrate after joining a silicon substrate The figure which shows the LED array described in patent document 1 The figure which shows the surface emitting laser apparatus described in patent document 2 The figure which shows the surface emitting type diode array described in patent document 3

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... GaAs substrate 2 ... Separation layer 3 ... n-AlzGa1-zAs layer 4 ... n-AlxGa1-xAs layer 5 ... Active layer (n-AlyGa1-yAs layer)
6 ... p-AlxGa1-xAs layer 7 ... p-AlzGa1-zAs layer 8 ... insulating layer 9 ... contact window 10 ... one electrode (substrate side electrode)
DESCRIPTION OF SYMBOLS 11 ... Groove 12 ... Silicon substrate 13 ... Wiring pattern 14 ... The other electrode (light emission side electrode)
15 ... Window for light emission 16 ... Light emitting region 17 ... Thermally conductive pad

Claims (8)

A surface-emitting device constructed by providing a surface-emitting element on a substrate having a wiring pattern on the surface,
A radiation-side electrode having a window for emitting light from the light emitting portion of the surface-emitting element is formed on the light-emitting surface of the surface-emitting element, and the substrate-side electrode of the surface-emitting element The surface-emitting type device is characterized in that the wiring pattern of the substrate and the wiring pattern of the substrate are electrically connected at a portion other than directly below the light-emitting portion.   2. The light emitting portion of the surface-emitting element and the substrate are located directly below the light emitting portion but are not electrically connected, but there is a portion that is in thermal contact. A surface-emitting device according to claim 1.   2. The surface emitting device according to claim 1, wherein the electrical connection between the substrate side electrode of the surface emitting element and the wiring pattern of the substrate is performed by direct bonding of metals.   A plurality of the surface-emitting elements are arranged in a line to form a surface-emitting diode array, the substrate-side electrode of the surface-emitting diode is an individual electrode, and the radiation-side electrode is a plurality of surface emitting elements. The surface emitting device according to claim 1, wherein the surface emitting device is a common electrode of the type diode.   The surface-emitting device according to claim 1, wherein the surface-emitting element is a surface-emitting laser.   A display device comprising the surface-emitting device according to claim 1 as a component.   An LED printer head comprising the surface-emitting device according to claim 1 as a constituent element.   A printer comprising the LED printer head according to claim 7.

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