JP2013135052A - Semiconductor light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light-emitting device which enhances uniformity of a current in a main semiconductor region which is a light-emitting surface, and has an overvoltage protection element with improved reliability.SOLUTION: The semiconductor light-emitting device, having an overvoltage protective function, comprises: a silicon semiconductor substrate 1; a main semiconductor region for a light emitting element; a first electrode; and a second electrode. The silicon semiconductor substrate has a protection element formation region. The first electrode has a bonding pad electrode 20. An optical transparent conductive film 19 and an insulator film 17, formed in roughly a rectangular or roughly a square shape, are disposed on the main semiconductor region. A hole 17b is formed in the insulator film, and a bonding pad electrode part and the optical transparent conductive film are connected with a band shape connection conductive layer 22, formed so as to include the hole. The hole is so formed as to include at least a center of the bonding pad electrode and a central part of an outer peripheral edge corner of the optical transparent conductive film on a diagonal line of the optical transparent conductive film.

Description

The present invention relates to a semiconductor light emitting device with an overvoltage protection element such as a Schottky barrier diode, a pn junction diode, a varistor, or a capacitor.

  A semiconductor light emitting device with an overvoltage protection element is disclosed in Japanese Patent Laying-Open No. 2006-66863 (Patent Document 1) related to the present applicant. A semiconductor light emitting device disclosed herein includes a silicon semiconductor substrate, a light emitting semiconductor region formed of a plurality of nitride semiconductor layers formed thereon, a light-transmitting conductive film formed on a surface of the light emitting semiconductor region, A bonding pad electrode connected to the light transmissive conductive film, a substrate electrode formed on the bottom surface of the semiconductor substrate, and an overvoltage protection element formed in or on the semiconductor substrate. Since the overvoltage protection element is disposed under the bonding pad electrode, it is possible to protect the light emitting diode from overvoltage while suppressing an increase in the size of the semiconductor light emitting device.

  By the way, the light-transmitting conductive film functions to flow a current to the outer peripheral side portion of the light emitting semiconductor region than the bonding pad electrode. In order to obtain this function satisfactorily, it is desirable that the light-transmitting conductive film has a low electrical resistance and a high light-transmitting property. However, indium / tin / oxide (hereinafter referred to as ITO) generally used as a light-transmitting conductive film has a higher resistivity than a metal film. Further, since ITO does not have 100% light transmittance, it is formed as thin as possible. Accordingly, the sheet resistance of the light-transmitting conductive film made of ITO is relatively large, and it is difficult to sufficiently pass the current to a portion of the light emitting semiconductor region away from the bonding pad electrode. Even when the light-transmitting conductive film is formed of a material other than ITO, it is difficult to satisfy both the light transmitting property and the conductivity.

In order to solve the above problem, Japanese Patent Application Laid-Open No. 2007-311506 (Patent Document 2) discloses the following technique. The silicon semiconductor substrate has a light emitting element main semiconductor region, a first electrode, and a second electrode. The silicon semiconductor substrate has a protective element formation region, and the first electrode has a bonding pad electrode. In plan view, the protective element forming region is disposed inside the bonding pad portion, the light-transmitting conductive film and the insulating film are disposed on the main semiconductor region, and further, a hole is formed in the insulating film. The bonding pad electrode portion and the light-transmitting conductive film are connected by a strip-shaped connection conductor layer formed so as to include a hole.
With this configuration, it is possible to reduce the size of the semiconductor light emitting device with an overvoltage protection element and to make the current in the main semiconductor region uniform.

JP 2006-66863 A JP 2007-311506 A

  The present invention is a further improvement of the above-described prior art, and its purpose is to further increase the uniformity of the current in the main semiconductor region serving as the light emitting surface and further improve the reliability in a semiconductor light emitting device with an overvoltage protection element. An object of the present invention is to provide a semiconductor light emitting device.

In order to solve the above problems, the present invention provides:
A substrate having one main surface and the other main surface and having conductivity; a first main surface from which light can be extracted; and the one main surface of the substrate opposite to the first main surface. A second main surface electrically and mechanically coupled to the main surface and including a plurality of semiconductor layers for generating light and from the first main surface to the second main surface A main semiconductor region having a first hole penetrating the surface; a bonding pad electrode covering the first hole and covering a part of the first main surface of the main semiconductor region; A substrate electrode formed on the substrate; an overvoltage protection element disposed between the bonding pad electrode and the other main surface of the substrate and electrically connected to both the bonding pad electrode and the substrate electrode; Formed in a substantially rectangular or substantially square shape on the one main surface of the main semiconductor region. A light transmissive conductive film; a first portion disposed between the bonding pad electrode and the one main surface of the main semiconductor region; and the bonding electrode and the one main surface of the main semiconductor region. And a second portion that is continuous with the first portion and covers at least a part of the light transmissive conductive film, and the second portion includes the light. A light-transmissive insulating film provided with a second hole for exposing the transparent conductive film, and a coating covering a part of the surface of the insulating film in a strip shape and connected to the bonding pad electrode And a filling portion that is filled in the second hole of the insulating film and that is continuous with the covering portion and connected to the light-transmissive conductive film, and is light transmissive Made of conductive material with lower resistivity than conductive film And the second hole has at least a center portion of the center of the bonding pad electrode and an outer peripheral corner portion of the light transmissive conductive film on a diagonal line of the light transmissive conductive film. It is formed so that it may contain.

In a semiconductor light emitting device with an overvoltage protection element, it is possible to provide a semiconductor light emitting device in which the current in the main semiconductor region serving as the light emitting surface is further uniformized and the reliability is further improved.

It is a top view which shows schematically the semiconductor light-emitting device which has the conventional overvoltage protection function. It is a longitudinal cross section of the AA direction of the semiconductor light-emitting device which has the conventional overvoltage protection function. It is a top view which shows roughly the semiconductor light-emitting device which has the overvoltage protection function of this invention.

Next, embodiments of the present invention will be specifically described with reference to the drawings. In addition, embodiment shown here is an example and this invention is not the meaning limited to embodiment shown here.

FIG. 3 is a top view of a semiconductor light emitting device with an overvoltage protection element according to the first embodiment of the present invention, that is, a composite semiconductor device of a light emitting diode and a Schottky barrier diode as an overvoltage protection element. FIG. 1 is a top view of a conventional semiconductor light emitting device having an overvoltage protection function. In the conventional semiconductor light emitting device having an overvoltage protection function and the light emitting device according to Example 1, the positions and shapes of the strip-like connection conductor layer 22 and the second hole 17b are different in a top view.
In the conventional semiconductor light emitting device of FIG. 1, the four strip-like connection conductor layers 22 and the second holes 17 b extending from the bonding pad electrode 20 to the outer peripheral edge are formed on the rectangular silicon semiconductor substrate 1 in the vicinity of the bonding pad electrode 20. One is formed on a diagonal line of the light-transmitting conductive film 19 formed in a substantially rectangular shape, bent in the middle toward the outer peripheral edge, and formed to extend toward the two opposite sides.
On the other hand, the band-shaped connecting conductor layer 22 and the second hole 17b of the semiconductor light emitting device with the overvoltage protection element according to the first embodiment of the present invention are formed from the bonding pad electrode 20 to the silicon semiconductor substrate 1 as is apparent from FIG. The light-transmitting conductive film 19 formed in a substantially square shape extends in a straight line toward the outer peripheral edge on the diagonal line. Although the silicon semiconductor substrate 1 according to Example 1 of the present invention is substantially square, it may be substantially rectangular.
The other configuration of the semiconductor light emitting device with the overvoltage protection element according to the first embodiment of the present invention is the same as the configuration of the conventional semiconductor light emitting device having an overvoltage protection function shown in FIG.
Hereinafter, each part will be described in detail.

The semiconductor substrate 1 is made of a p-type single crystal silicon substrate containing a group 3 element such as boron as an impurity for determining the conductivity type, and has one main surface 5 and the other main surface 6 and a protective element forming region at the center. 7. The p-type impurity concentration of the semiconductor substrate 1 is, for example, about 5 × 10 ^{18 to} 5 × 10 ¹⁹ cm ^−3, and the resistivity is about 0.0001Ω · cm to 0.01Ω · cm. Therefore, the semiconductor substrate 1 is a conductive substrate and functions as a current path for the light emitting element and the protection element. That is, the protection element formation region 7 in the center of the semiconductor substrate 1 functions as a main portion of the Schottky barrier diode and also functions as a current path, and the outer region 8 surrounding the protection element formation region 7 of the semiconductor substrate 1 emits light. It functions as a current path for the element. Furthermore, the semiconductor substrate 1 has a function as a substrate for epitaxial growth of the main semiconductor region 2 and a function as a support for the main semiconductor region 2 and the first electrode 3 for constituting a light emitting element. The preferred thickness of the semiconductor substrate 1 is relatively thick 100 to 500 μm. As is clear from FIG. 2, a step is formed in the outer peripheral portion of one main surface 5 of the semiconductor substrate 1 and a recess 9 is formed in the center, but the entire one main surface 5 of the semiconductor substrate 1 is formed. It can be flat. In addition, the conductivity type of the semiconductor substrate 1 can be n-type. Further, the impurity concentration of the outer region 8 of the semiconductor substrate 1 is made higher than that of the protective element forming region 7, thereby making the resistivity of the outer region 8 lower than that of the protective element forming region 7. The voltage drop in the region 8 can be reduced.

The main semiconductor region 2 for constituting the main part of the light-emitting element has a plurality of layers made of a group 3-5 compound semiconductor different from the silicon semiconductor substrate 1, and is well-known vapor phase growth on the silicon semiconductor substrate 1. Formed by the law. More specifically, the main semiconductor region 2 has an n-type buffer layer 10, an n-type semiconductor layer 11, an active layer 12, and a p-type semiconductor layer 13 in order to form a double heterojunction light emitting diode. . The n-type semiconductor layer 11 may be referred to as an n-type cladding layer, and the p-type semiconductor layer 13 may be referred to as a p-type cladding layer. In principle, the light emitting diode can be composed of only the n-type semiconductor layer 11 and the p-type semiconductor layer 13. Therefore, one or both of the n-type buffer layer 10 and the active layer 12 can be omitted from the main semiconductor region 2. Further, a known current distribution layer or ohmic contact layer can be added to the main semiconductor region 2 as necessary. The first main surface 14 and the second main surface 15 of the main semiconductor region 2 extend in parallel to the semiconductor substrate 1. The first main surface 14 of the main semiconductor region 2 has a function as a surface for extracting light generated in the active layer 12 to the outside. The second main surface 15 of the main semiconductor region 2 is electrically and mechanically coupled to the semiconductor substrate 1.

The main semiconductor region 2 has a hole 16 penetrating from the first main surface 14 to the second main surface 15 at substantially the center thereof. The hole 16 is continuous with the recess 9 of the silicon semiconductor substrate 1. The hole 16 and the recess 9 are formed by etching after the main semiconductor region 2 is epitaxially grown on the silicon semiconductor substrate 1 before the recess 9 is formed. For this reason, the alloying layer generated between the silicon semiconductor substrate 1 and the main semiconductor region 2 is removed, and silicon is exposed on the surface of the recess 9 of the silicon semiconductor substrate 1. The wall surfaces of the hole 16 and the recess 9 are inclined so as to taper from the first main surface 14 to the second main surface 15 of the main semiconductor region 2. The recess 9 of the silicon semiconductor substrate 1 is provided in the protective element formation region 7.

The first electrode (upper electrode) 3 includes a light transmissive conductive film 19, a bonding pad electrode 20, and a strip-like connection conductor layer 22. The bonding pad electrode 20 is connected to the light-transmitting conductive film 19 through the strip-shaped connection conductor layer 22 and is also connected to the Schottky contact metal layer 18. Therefore, the bonding pad electrode 20 has a cathode function of a Schottky barrier diode in addition to an anode function of the light emitting diode.

The light transmissive conductive film 19 is disposed on almost the entire first main surface 14 of the main semiconductor region 2, that is, the surface of the p-type semiconductor layer 13, and is in ohmic contact therewith. Therefore, as already described, the light-transmitting conductive film 19 contributes to flowing a current uniformly through the main semiconductor region 2 and enables extraction of light emitted from the main semiconductor region 2. The light transmissive conductive film 19 of this embodiment is made of ITO (indium / tin / oxide) having a thickness of about 1800 angstroms. The light-transmitting conductive film 19 can be formed of a material selected from Ni, Pt, Pd, Rh, Ru, Os, Ir, Au, Ag, and the like other than ITO. However, it is necessary to increase the light transmittance of the light transmissive conductive film 19 in any case, and the light transmissive conductive film 19 cannot be formed too thick. It is formed to about 5000 angstroms, preferably about 1800 angstroms. When the light-transmitting conductive film 19 is formed thin, the sheet resistance of the light-transmitting conductive film 19 is inevitably increased, and a sufficient amount of current can be passed through the portion of the main semiconductor region 2 away from the bonding pad electrode 20. Can not. In order to solve this problem, a strip-like connection conductor layer 22 is provided. The strip-shaped connection conductor layer 22 electrically connects the light-transmitting conductive film 19 and the bonding pad electrode 20 and contributes to the improvement of current uniformity in the main semiconductor region 2.

The insulating film 17 includes most of the light-transmitting conductive film 19, the first main surface 14 and side surfaces not covered with the light-transmitting conductive film 19 in the main semiconductor region 2, and part of the wall surface and bottom surface of the recess 9. Covering.

  In order to obtain the above function, the insulating film 17 is made of a material having better light transmission than the light transmissive conductive film 19, for example, silicon oxide (SiO 2), the light transmissive conductive film 19, the main semiconductor region 2, and the semiconductor substrate 1. It is formed so as to cover the surface. Since the insulating film 17 is made of a material (SiO 2) having better light transmission than the light transmissive conductive film 19, the thickness can be set to, for example, 1500 to 10000 angstroms thicker than that of the light transmissive conductive film 19. The insulating film 17 has a first hole 17 a filled with a Schottky contact metal layer 18 at the center thereof, and a plurality (four) of the insulating film 17 extends from the bonding pad electrode 20 to the outer peripheral direction of the light transmissive conductive film 19 in a band shape. Second hole 17b.

As shown in FIG. 3, the belt-like second holes 17b are formed in a straight line along a substantially diagonal line of the light transmissive conductive film 19 formed in a substantially square shape. At this time, it is desirable that the second hole 17 b is formed at an intermediate position between the center of the bonding pad electrode 20 and the outer peripheral corner of the light transmissive conductive film 19 on a substantially diagonal line of the light transmissive conductive film 19. .
Further, it is desirable that one end of the band-shaped second hole 17 b is as close as possible to the bonding pad electrode 20, and the other end of the band-shaped second hole 17 b is as close as possible to the outer peripheral edge of the light-transmitting conductive film 19. The width of the band-shaped second hole 17b is narrower than the band-shaped connecting conductor layer 22 and is as narrow as possible within a range in which electrical connection between the bonding pad electrode 20 and the light-transmitting conductive film 19 by the band-shaped connecting conductor layer 22 can be secured. For example, it is determined to be about 2 μm to 10 μm. Note that the second hole 17b for electrical connection between the bonding pad electrode 20 and the light-transmitting conductive film 19 is provided outside the bonding pad electrode 20 except under the bonding pad electrode 20, and the second hole 17b of the insulating film 17 is provided. Since the portion not having the hole 17b is disposed between the bonding pad electrode 20 and the main semiconductor region 2, the stress generated in the main semiconductor region 2 based on the bonding pad electrode 20 is suppressed well by the insulating film 17. Has been.

As is apparent from FIG. 3, four strip-like connection conductor layers 22 are provided corresponding to the four second holes 17 b of the insulating film 17. Each strip-shaped connecting conductor layer 22 has a strip-shaped covering portion 24 disposed on the insulating film 17 and a filling portion 25 disposed in the second hole 17b. The filling portion 25 is electrically connected to the light transmissive conductive film 19. The strip-shaped connecting conductor layer 22 is formed of a material having a lower resistivity than the light transmissive conductive film 19 and has a sheet resistivity lower than that of the light transmissive conductive film 19. In this embodiment, Au (gold) is vapor-deposited to about 2500 to 100,000 angstroms in the entire upper surface of the insulating film 17 and in the second hole 17b, and then unnecessary portions are removed by etching to form the strip-like connecting conductor layer 22. Has been. Since the filling portion 25 of the band-shaped connection conductor layer 22 extends from the bonding pad electrode 20 to the vicinity of the outer peripheral end of the light transmissive conductive film 19, it is formed in the main semiconductor region 2 including the active layer 12 through the light transmissive conductive film 19. This contributes to a good dispersion of the current. Further, since the band-shaped connecting conductor layer 22 is formed corresponding to the second hole 17b formed in a straight line along the substantially diagonal line of the light-transmitting conductive film 19, the band-shaped connecting conductor layer 22 is bent as shown in FIG. Compared to the conventional semiconductor light emitting device having the conductor layer 22, the current in the main semiconductor region 2 serving as the light emitting surface is more uniform, and the light emission output is improved. Further, since the current concentration in the main semiconductor region 2 is further improved, the reliability is also improved.

The Schottky contact metal layer 18 functioning as a Schottky electrode is, for example, Ti, Pt, Cr, Al
, Sm, PtSi, Pd ₂ Si, or the like, and the first hole 1 of the insulating film 17
The surface of the recess 9 of the silicon semiconductor substrate 1 is in Schottky contact via 7a. A Schottky diode as a protection element is formed by the protection element formation region 7 of the semiconductor substrate 1 and the Schottky contact metal layer 18. The Schottky contact metal layer 18 is disposed inside the bonding pad electrode 20 in plan view. Therefore, an increase in the area of the semiconductor substrate 1 and the main semiconductor region 2 is suppressed by providing a Schottky diode as a protective element.

The bonding pad electrode 20 is made of a material having a lower resistivity than the light transmissive conductive film 19 (for example, A
u, Ni) and is connected to the Schottky contact metal layer 18 and the strip-like connection conductor layer 22.

The second electrode (substrate electrode) 4 is made of a metal layer and is formed on the entire other main surface 6 of the semiconductor substrate 1. That is, the second electrode 4 is in ohmic contact with the lower surfaces of both the protective element forming region 7 and the outer peripheral region 8 of the semiconductor substrate 1.

DESCRIPTION OF SYMBOLS 1 Silicon semiconductor substrate 2 Main semiconductor area | region 3 1st electrode 4 2nd electrode 7 Protection element formation area 17 Insulating film 17b 2nd hole 19 Optically transparent conductive film 22 Band-shaped connection conductor layer

Claims (2)

A substrate having one main surface and the other main surface and having conductivity;
A first main surface from which light can be extracted and a second main surface facing the first main surface and electrically and mechanically coupled to the one main surface of the substrate; A main semiconductor region having a first hole penetrating from the first main surface to the second main surface;
A bonding pad electrode covering the first hole and covering a part of the first main surface of the main semiconductor region;
A substrate electrode formed on the substrate;
An overvoltage protection element disposed between the bonding pad electrode and the other main surface of the substrate and electrically connected to both the bonding pad electrode and the substrate electrode;
A light transmissive conductive film formed in a substantially rectangular or substantially square shape on the one main surface of the main semiconductor region;
A first portion disposed between the bonding pad electrode and the one main surface of the main semiconductor region, and a gap between the bonding electrode and the one main surface of the main semiconductor region; A second portion that is continuous with the first portion and covers at least a part of the light transmissive conductive film, and for exposing the light transmissive conductive film to the second portion. A light transmissive insulating film provided with the second hole, and
A part of the surface of the insulating film is covered in a strip shape and is filled in the second hole of the covering part connected to the bonding pad electrode and the insulating film, and is continuous with the covering part. And a connecting conductor layer formed of a conductive material having a resistivity lower than that of the light transmissive conductive film, and a filling portion connected to the light transmissive conductive film.
The second hole is formed so as to include at least a center portion of the center of the bonding pad electrode and a corner portion of an outer peripheral edge of the light transmissive conductive film on a diagonal line of the light transmissive conductive film. A semiconductor light-emitting device. 2. The semiconductor light emitting device according to claim 1, wherein the second hole is formed in a straight line along a diagonal line of the light transmissive conductive film.