JPH0531317B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field The present invention relates to a light emitting semiconductor device and a method for manufacturing the same, and particularly relates to a light emitting semiconductor device that extracts light from a substrate surface and a method for manufacturing the same. (B) Prior Art Generally, in a light emitting semiconductor element that extracts light from the surface of a semiconductor substrate, a bonding pad is formed as a front electrode approximately in the center of the light emitting surface, and a back electrode is formed on the back surface of the substrate. Since the bonding pad is wire bonded to the bonding pad, it is necessary to form the bonding pad relatively large. For example, when this type of light emitting semiconductor element is actually used, current is concentrated directly under the bonding pad, so that only the area around the bonding pad tends to emit light. That is, since it is difficult for the current to spread uniformly across the light emitting surface, a problem arises in that the outer periphery of the light emitting surface becomes relatively dark. Furthermore, since light is blocked by the bonding pad,
Another problem was that the luminescence was not used effectively. In order to solve the above-mentioned problems, a light emitting semiconductor device has been proposed in Japanese Utility Model Application No. 78473/1983. The structure is such that in a light emitting semiconductor element in which a lead wire is bonded to an electrode formed on a semiconductor substrate, an insulating layer is interposed between the center of the electrode and the semiconductor substrate to increase the spread of current. However, in the above-mentioned light-emitting semiconductor device, the insulating layer formed at the center of the surface of the light-emitting layer (P-N junction) is made of, for example, Al ₂ O ₂ or SiO ₂ , and therefore the insulating layer is different from the light-emitting layer. The problem is that the adhesion is very poor. Therefore, in the wire bonding process of the light emitting semiconductor device, after first bonding to the bonding pad, when pulling the gold wire through the capillary to the lead terminal, the first bonding pad and its lower part are Even the insulating layer of the product may peel off. That is, there is a drawback that the yield and reliability of the product are reduced. (c) Purpose This invention allows current to flow to every corner of the light emitting surface,
It is an object of the present invention to provide a light-emitting semiconductor element that improves the efficiency of extracting light from a light-emitting surface. (d) Configuration The method for manufacturing a light emitting semiconductor device according to the present invention includes:
A method for manufacturing a light emitting semiconductor device in which an electrode layer is formed on a light emitting surface via an ohmic contact layer made of a semiconductor, the method comprising: a light emitting layer, an ohmic contact layer, and a conductivity type opposite to that of the ohmic contact layer. Bonding is performed by forming a current blocking layer made of a semiconductor on the surface of a semiconductor substrate by molecular beam epitaxial growth (MBE), and etching the current blocking layer using a patterned positive resist as a mask. forming a contact hole in the electrode layer excluding the pad;
exposing a bonding pad portion of the resist to remove the resist in that portion;
A step of vapor depositing an electrode material on the surface of the semiconductor substrate, and a step of forming a bonding pad and an electrode layer connected thereto by lifting off the remaining resist on the surface of the substrate and the electrode material on this surface. It is characterized by having the following. (E) Embodiment FIG. 1 is a perspective view schematically showing an embodiment of a light emitting semiconductor device according to the present invention. Reference numeral 1 denotes a substantially rectangular light emitting semiconductor element, which has a double heterojunction structure. Specifically, a relatively thin N-type GaAs layer 21 is formed on the surface of the substrate 10 made of N-type GaAs, and a relatively thick N-type Ga _0.3 Al _0.7 As layer 22 is formed on top of the relatively thin N-type GaAs layer 21. A thin P-type Ga _0.7 Al _0.3 As layer 23 is formed, and a relatively thick P-type Ga _0.3 Al _0.7 layer is formed on top of this layer 23.
A light emitting layer 20 is formed in which As layers 24 are laminated, respectively. Furthermore, the P-type Ga _0.3 Al _0.7 As layer 2
An ohmic contact layer 25 made of P-type GaAs with a high carrier concentration is formed on the surface of 4 in an appropriate pattern. Reference numeral 30 denotes a substantially circular current blocking layer made of N-type GaAs having a conductivity type opposite to that of the ohmic contact layer 25 (reverse polarity). This current blocking layer 30 is arranged approximately at the center of the substrate 10 and above the ohmic contact layer 25. The layers forming the light emitting semiconductor device 1 and the current blocking layer 30 described above are also grown continuously by a so-called molecular beam epitaxial growth method (MBE apparatus). On the surface of the substrate 10, an electrode layer 40 and a bonding pad 41 made of, for example, Ti-Au or Al are formed. Note that the electrode layer 40 and bonding pad 41 are shaped to spread the current.
Specifically, as shown in FIG.
A straight line portion extending from the substantially circular bonding pad 41 adhered to the surface of the substrate 41 on a diagonal line of the board so that the tip is located near the corner of the board; The electrode layer 40 is formed from rectangular annular portions of similar shapes arranged such that their corner portions are located at the respective corners. 42 is a back electrode made of, for example, Au-Ge;
It is attached to the back surface of the substrate 10. FIG. 2 is an explanatory diagram showing an embodiment of the manufacturing method according to the present invention (taken along the line A-A' in FIG. 1). In this figure, the same parts as in FIG. 1 are indicated by the same reference numerals. (a) N-type GaAs layer 21 on the surface of the semiconductor substrate 10,
A light-emitting layer 20 consisting of an N-type Ga _0.3 Al _0.7 As layer 22, a P-type Ga _0.7 Al _0.3 As layer 23, a P-type Ga _0.3 Al _0.7 As layer 24, an ohmic contact layer 25 consisting of P-type GaAs, and the optical Microcontact layer 2
A current blocking layer 30 and the like made of N-type GaAs, which is a conductivity type opposite to that of No. 5, are continuously grown using a molecular beam epitaxial growth method (MBE apparatus). (b) A positive resist 50 is applied to the surface of the semiconductor substrate 10 on which each of the layers described above has been formed. Next, the resist 50 corresponding to a portion of the electrode layer 40 excluding the bonding pad where a contact hole is to be formed is exposed, and then developed to remove the exposed portion of the resist 50. (c) By selectively etching the current blocking layer 30 using the resist 50 as a mask, a contact hole is formed in the electrode layer 40 excluding the bonding pad. (d) Only the center of the resist 50 (portion A in the figure) is exposed again. Thereafter, the exposed portions of the resist 50 are removed by development, thereby exposing the portions of the current blocking layer 30 to which the bonding pads will be deposited. (e) Electrode material 4 such as Ti-Au on the surface of the substrate.
0' is formed by vapor deposition. (f) By lifting off the remaining resist 50 and the electrode material 40' on this surface, the remaining resist 50 and the electrode material 40' on this surface are removed, so that the electrode layer 40 and bonding pad 41 are removed. It is formed. (g) Using the electrode layer 40 and bonding pad 41 as a mask, the ohmic contact layer 25 is selectively etched. Next, on the back side of the board 10
The back electrode 42 is formed by vapor deposition of an electrode material such as Au-Ge. The table below shows the hole measurement results of Ga _{1-X Al}

[Table] Degree and ρ are specific resistance.
Note that the shape of the electrode layer 40 is not limited to the above-described embodiment, and may be any shape that spreads the current. Further, in the above embodiment, each layer forming the light emitting semiconductor element has a double heterojunction structure, but the present invention is of course not limited to this. Although the above-described embodiments have been described using a light-emitting semiconductor device made of GaAlAs, the present invention is not limited thereto, and can be applied to light-emitting semiconductor devices that are likely to cause current concentration. (F) Effect The light-emitting semiconductor device according to the present invention is a method for manufacturing a light-emitting semiconductor device in which an electrode layer is formed on a light-emitting surface via an ohmic contact layer made of a semiconductor. A process of forming an ohmic contact layer and a current blocking layer made of a semiconductor of the opposite conductivity type on the surface of a semiconductor substrate by molecular beam epitaxial growth (MBE), and using a patterned positive resist as a mask to form a current blocking layer made of a semiconductor of the opposite conductivity type. a step of forming a contact hole in the electrode layer excluding the bonding pad by etching the blocking layer; a step of exposing the bonding pad portion of the resist to remove the resist in that portion; and forming a bonding pad and an electrode layer connected thereto by lifting off the remaining resist on the surface of the substrate and the electrode material on this surface. It is characterized by Therefore, according to the present invention, since a self-alignment method is used, the process can be simplified, and the current blocking layer has the same shape as the electrode, so the aluminum electrode does not protrude outside, resulting in a reduction in the amount of light emitted. There's nothing to do. Furthermore, since the light emitting layer, ohmic contact layer, and electrode blocking layer are formed by MBE, the thickness of each layer can be easily controlled and a desired device can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view schematically showing an embodiment of a light emitting semiconductor device according to the present invention, and FIG. 2 is an explanatory diagram schematically showing an embodiment of the manufacturing method according to the present invention. 1... Light emitting semiconductor element, 10... Semiconductor substrate,
20... Light emitting layer, 25... Ohmic contact layer, 30... Current blocking layer, 40... Electrode layer, 41
...bonding pad.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a light emitting semiconductor device in which an electrode layer is formed on a light emitting surface via an ohmic contact layer made of a semiconductor, comprising: a light emitting layer, an ohmic contact layer, and the ohmic contact layer. A step of forming a current blocking layer made of a semiconductor of an opposite conductivity type on the surface of a semiconductor substrate by molecular beam epitaxial growth (MBE), and etching the current blocking layer using a patterned positive resist as a mask. forming a contact hole in the electrode layer excluding the bonding pad; exposing the bonding pad portion of the resist to remove the resist in that portion; and depositing an electrode material on the surface of the semiconductor substrate. and a step of forming a bonding pad and an electrode layer connected thereto by lifting off the remaining resist on the surface of the substrate and the electrode material on this surface. A method for manufacturing a light emitting semiconductor device.