JPH11121803A - Light emitting diode and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light emitting diode, together with its manufacturing method, comprising an electrode which is excellent in bondability and adhesion. SOLUTION: After a first electrode 11 is formed, a pattern wherein the diameter of an electrode is smaller than the first electrode 11 is formed when a photo- pattern for a second electrode 12 is formed, so that the second electrode 12 does not contact an epitaxial layer 5. Thus, the electrodes 11 and 12 excellent in bondability and adhesion are formed. When considering an adhesion material for the second electrode 12, adhesion to the surface of a glass, etc., as well as a semiconductor surface is not required to be considered, so adhesion only to the first electrode 11 is required to be considered, widening a range for selecting electrode material. Even if a vapor-deposition film of adhesion material for the second electrode 12 is formed on the vapor-deposition film of metal material for the first electrode 11, and the first electrode 11 and the second electrode 12 are formed at the same time by etching, the second electrode 12 does not contact the epitaxial layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a light emitting diode and a method for manufacturing the same.

[0002]

2. Description of the Related Art Bondability is a factor that affects the quality of a semiconductor device. The bondability refers to, for example, the strength (separability) and positional accuracy of wire bonding between the electrode of the light emitting diode and the substrate when the light emitting diode is mounted on the substrate. Bondability is improved by forming a layer of an adhesive material made of a metal suitable for wire bonding on the electrode.

FIG. 4 is a sectional view of an AlGaAs-based light emitting diode having a double heterostructure.

A p-type AlGaAs cladding layer 2 is formed on a p-type GaAs substrate 1 shown in FIG.
Three epitaxial layers (hereinafter referred to as “epi layers”) 5 of a p-type AlGaAs active layer 3 and an n-type AlGaAs window layer 4 are formed. AuZ on the entire back surface of the substrate 1
An n / Ni / Au back electrode 6 is formed, a first electrode 7 is formed at the center of the surface of the epi layer 5, and a second electrode 8 is formed so as to cover the first electrode 7. The substrate 1, the epi layer 5, and the electrodes 6, 7, 8 constitute a light emitting diode 9. p-type AlGaAs active layer 3 and n-type AlGaAs
The pn interface of the window layer 4 is a light emitting layer.

In this light emitting diode 9, ohmic contact is ensured by the first electrode 7, and good bondability is obtained by the second electrode 8.

The first electrode (circular AuGe / Ni / Au electrode) 7 is provided on the surface of the epi layer 5 (hereinafter referred to as “epi surface”).
The second electrode (circular Ti / Au or Cr / Au or the like) 8 is formed on the first electrode 7 by a non-heat treatment so as to adhere to the first electrode such as Ti or Cr. It can be formed using a close contact material made of a good metal.

Generally, the second electrode is formed by a lift-off method as shown in FIGS. 5 (a) to 5 (d). FIG.
(A)-(d) is a process drawing which shows the manufacturing method of the light emitting diode shown in FIG.

[0008] Epi layer (n-type AlGaAs window layer 4)
5, a first electrode 7 is formed (FIG. 5A), and a photo pattern 10 is formed around the first electrode 7 (FIG. 5A).
(B)). Epi layer 5, first electrode 7, and photo pattern 1
0 from above, an adhesive material (Ti) made of metal for the second electrode 8
Alternatively, adhesion materials such as Cr) 8a and 8 are adhered by vapor deposition (FIG. 5C). By peeling off the photopattern 10 with a peeling agent, the extra adhesive material 8a deposited on the photopattern 10 is peeled off, and the second electrode 8 is formed so as to cover the first electrode 7. (FIG. 5 (d)).

[0009]

By the way, in the above-mentioned conventional method, the second electrode 8 is formed so as to cover the first electrode 7, so that the portion protruding from the surface of the first electrode 7 is
The epi layer 5 and the second electrode 8 come into direct contact.

However, the adhesion material of the second electrode 8 does not always have good adhesion to the epi surface of the light emitting diode.
When the adhesion to the epi surface is poor, although there is good adhesion to the first electrode, the separation occurs at the interface between the adhesion material of the second electrode 8 and the epi surface at the outer peripheral portion of the electrode, and this separation occurs. There is a problem that the portion adheres to the bonding electrode and hinders bonding.

It is an object of the present invention to solve the above-mentioned problems and to provide a light emitting diode having an electrode having good bondability and excellent adhesion, and a method of manufacturing the same.

[0012]

In order to achieve the above object, a light emitting diode according to the present invention is formed on a light emitting layer comprising a pn interface between a p-type semiconductor layer and an n-type semiconductor layer, and on one of the semiconductor layers. In a light-emitting diode including a first electrode for ensuring ohmic contact and a second electrode formed on the first electrode to improve bondability, the second electrode protrudes from the surface of the first electrode. It is formed so as not to exist.

Further, according to the method of manufacturing a light emitting diode of the present invention, a light emitting layer comprising a pn interface between a p-type semiconductor layer and an n-type semiconductor layer is formed, and a first layer for ensuring ohmic contact on one of the semiconductor layers is formed. In a method for manufacturing a light emitting diode, in which an electrode is formed and a second electrode for improving bondability is formed on the first electrode, the first electrode is formed on the p-type semiconductor layer, and then the first electrode is formed. Surrounded by a second electrode photo pattern having an opening smaller than the first electrode, and after depositing an adhesive material made of a metal for the second electrode, the second pattern is lifted off using a lift-off method of peeling off the second electrode photo pattern. A second electrode is formed on one electrode.

Further, according to the method for manufacturing a light emitting diode of the present invention, a light emitting layer comprising a pn interface between a p-type semiconductor layer and an n-type semiconductor layer is formed, and a first layer for securing ohmic contact on any one of the semiconductor layers is provided. In a method for manufacturing a light emitting diode, in which an electrode is formed and a second electrode for improving bondability is formed on the first electrode, an adhesion material made of a metal for the first electrode is deposited on the p-type semiconductor layer. After performing heat treatment and further vapor-depositing an adhesive material made of a metal for the second electrode on the entire surface, the first electrode and the second electrode are formed by etching.

According to the present invention, after forming the first electrode on any of the semiconductor layers, a pattern having a smaller electrode diameter than the first electrode is formed by a lift-off method when forming a photo pattern for the second electrode. Thus, when the adhesive material made of the metal for the second electrode is deposited, it is prevented from wrapping around to a portion other than the surface of the first electrode, that is, the second electrode is prevented from contacting the semiconductor layer. Therefore, an electrode having good bondability and excellent adhesion can be formed. Also,
When examining the adhesion material made of metal for the second electrode, it is not necessary to consider not only the semiconductor surface, but also the adhesion to other surfaces such as a glass surface, and only the adhesion to the first electrode may be considered. Therefore, the frame for selecting the electrode material is expanded. further,
Forming a deposited film of an adhesive material made of a metal for a second electrode on a deposited film of an adhesive material made of a metal for a first electrode, and forming the first electrode and the second electrode at the same time by etching. The electrode does not come into contact with the semiconductor layer.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1A is a sectional view showing an embodiment of the light emitting diode of the present invention, and FIG.
It is a top view of (a). The same members as those of the conventional example shown in FIG.

On a p-type GaAs substrate 1, a p-type AlGaAs
s cladding layer 2, p-type AlGaAs active layer 3, and n-type A
Three epi layers 5 composed of the lGaAs window layer 4 are formed. A circular first electrode 11 is formed at the center of the surface of the epi layer 5, and a second electrode 12 is formed on the first electrode 11. On the back surface of the substrate 1, a back electrode 6 is formed. The substrate 1, the epi layer 5, and the electrodes 6, 1
The light emitting diode 13 is constituted by 1 and 12.

Next, a method for manufacturing this light emitting diode will be described.

FIGS. 2A to 2D show FIGS. 1A and 1B.
FIG. 7 is a process chart showing a method for manufacturing the light emitting diode shown in FIG.

First, on a p-type GaAs substrate 1, a p-type Al
GaAs cladding layer 2, p-type AlGaAs active layer 3, n
An epitaxial layer 5 is formed by epitaxially growing three layers of the type AlGaAs window layer 4. The p-type AlGaAs cladding layer 2 has, for example, a mixed crystal ratio of 0.3, a thickness of 40 μm,
The carrier concentration is 5 × 10 ¹⁷ cm ⁻³ . p-type AlGa
The As active layer 3 has a mixed crystal ratio of 0.03 and a thickness of 1.0 μm.
m, the carrier concentration is 2 × 10 ¹⁸ cm ⁻³ .

The surface of the epi layer 5 has an electrode diameter of about 130 μm.
A first electrode (circular AuGe / Ni / Au electrode) 11 having a thickness of about 2,000 angstroms is formed by a lift-off method or etching. A back electrode (AuZn / Ni / Au electrode) 6 is formed on the entire back surface of the substrate 1 (FIGS. 1 and 2A).

A first electrode pattern for lift-off (photo pattern, not shown) is formed on the surface of the epi layer 5, an adhesion material for the first electrode 11 is deposited on the entire surface, and after heat treatment, the photo pattern is removed. Electrode (circular AuGe / Ni / Au electrode) 1 that secures ohmic contact by performing
1 is formed (FIG. 2A).

After the first electrode 11 is formed, a lift-off second electrode pattern (photo pattern) having an electrode diameter between 50 μm and 150 μm and smaller than the electrode diameter of the first electrode 11 is formed on the surface of the epi layer 5. 2) (FIG. 2)
(B)).

After the photo pattern 14 is formed, Cr, which serves as an adhesive material 12a for the second electrode 12, is deposited to a thickness of about 100
Vapor deposition is performed until the thickness reaches 0 Å, and Au is further deposited until the thickness becomes approximately 10,000 Å (FIG. 2C).

After the adhesion material 12a for the second electrode 12 is deposited, the photo-patterns 14 in the portions other than the portion to be the second electrode 12 are peeled off together with the adhesion material 12a by a lift-off method. The electrode diameter is 50 μm on top
The second electrode 12 having a size of between 150 μm and 150 μm is formed. As a result, a light emitting diode in which the second electrode 12 does not contact the epi layer 5 is obtained (FIG. 2D).

FIG. 3 is a diagram showing the correlation between the diameter of the second electrode in the light emitting diode, the number of bonding defects during wire bonding, and the cause of the failure.

In the figure, the horizontal axis indicates the electrode diameter of the bonding pad, and the vertical axis indicates the rate of occurrence of wire bonding failure. In the figure, circles indicate failures due to the ball shear test, and triangles indicate failures due to the inhibition of bonding.

As shown in FIG. 2, when the electrode diameter of the second electrode is 50 μm, bondability failure due to displacement from the bonding pad at the time of ball hitting occurs 30%, but when the electrode diameter of the second electrode is 80 μm. In that case it was reduced to 10%. When the electrode diameter of the second electrode was 100 μm, the bondability defect was 1-2%, which was almost negligible. Incidentally, when the electrode diameter of the second electrode was 130 μm or more, there were 50% of the cases where the poor adhesion portion between the outer peripheral portion of the second electrode and the epi surface adhered to the bonding electrode and the bonding was hindered. . The bonding failure refers to a bonding failure of 70 g or less in the ball shear test, and the wire bonding failure occurrence ratio is a percentage of the number of bonding failure chips to the number of light emitting diodes subjected to the bonding shear test.

The optimum condition in this embodiment is that the diameter of the second electrode is 100 μm or more and smaller than the diameter of the first electrode.

In this embodiment, the lift-off method is used. However, the present invention is not limited to the lift-off method. An adhesive material made of a metal for a first electrode is deposited on the entire surface of the epi, and heat treatment is performed. Even if the electrode pattern is formed by etching after the entire surface of the adhesive material made of the metal for the two electrodes is deposited, the same effect can be obtained because the second electrode does not go around other than the first electrode surface.

As described above, according to the present invention, by forming the second electrode so as not to protrude from the surface of the first electrode, a light emitting diode having good bondability and having no peeling of the second electrode, and a method of manufacturing the same. Such an electrode structure can be used for forming an electrode pad in not only a light emitting diode but also any device that requires an electrode such as a laser diode or an IC. Also, the selection range of electrode materials for light emitting diodes and other devices is expanded.

[0033]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to provide a light emitting diode having electrodes having good bondability and excellent adhesion, and a method for manufacturing the same.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view showing one embodiment of a light emitting diode of the present invention, and FIG. 1B is a plan view of FIG.

FIGS. 2A to 2D are process diagrams showing a method for manufacturing the light emitting diode shown in FIGS. 1A and 1B.

FIG. 3 shows an electrode diameter of a second electrode in a light emitting diode;
FIG. 7 is a diagram showing a correlation between the number of bonding failures during wire bonding and the failure causes.

FIG. 4 is a cross-sectional view of a light-emitting diode having an AlGaAs double heterostructure.

FIGS. 5A to 5D are process diagrams showing a method for manufacturing the light emitting diode shown in FIG.

[Explanation of symbols]

 Reference Signs List 1 substrate (p-type GaAs substrate) 5 epitaxial layer (epi layer) 6 back electrode 11 first electrode 12 second electrode 12a adhesive material

Claims (3)

[Claims] 1. A light emitting layer comprising a pn interface between a p-type semiconductor layer and an n-type semiconductor layer, a first electrode formed on one of the semiconductor layers to ensure ohmic contact, and And a second electrode for improving bondability, wherein the second electrode is formed so as not to protrude from the surface of the first electrode. 2. A light emitting layer comprising a pn interface between a p-type semiconductor layer and an n-type semiconductor layer, and a first electrode for ensuring ohmic contact is formed on one of the semiconductor layers. In the method for manufacturing a light emitting diode for forming a second electrode for improving the bondability on the first, after forming a first electrode on the p-type semiconductor layer, the first electrode is smaller than the first electrode Surrounded by a second electrode photo pattern having an opening, and after depositing an adhesive material made of a metal for the second electrode, the upper surface of the first electrode is lifted off using a lift-off method of peeling the second electrode photo pattern. Forming a second electrode on the light emitting diode. 3. A light-emitting layer comprising a pn interface between a p-type semiconductor layer and an n-type semiconductor layer, and a first electrode for ensuring ohmic contact is formed on one of the semiconductor layers. In a method for manufacturing a light emitting diode, in which a second electrode for improving bondability is formed on a p-type semiconductor layer, an adhesion material made of a metal for a first electrode is deposited, and heat treatment is performed. A method for manufacturing a light-emitting diode, comprising: forming a first electrode and a second electrode by etching after an adhesive material made of a metal for two electrodes is entirely deposited.