JPH05110140A - Compound semiconductor optical device - Google Patents

Abstract

PURPOSE:To make the structure of the surface electrode of a light-emitting diode difficult to crack by stress at the time of wire bonding. CONSTITUTION:A p-type GaAlAs layer 2 and n-type GaAlAs layer 3 are formed on one surface side of a p-type GaAs substrate 1, and a ring-shaped ohmic junction metal 5, SiO2 layer 6 and a surface electrode covering the top surfaces of these ohmic junction metal 5 and SiO2 layer 6 and having a peripheral part composed of a bonding pad 7 connected with the ohmic junction metal 5 are formed on the surface of this n-type GaAlAs layer 3. Further, especially the bonding pad 7 is a multilayered structure composed of Mo layer and Al layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor optical device such as a surface emitting type light emitting diode, a semiconductor laser or a photodiode.

[0002]

2. Description of the Related Art As shown in FIG. 7, the structure of a surface-emitting type light emitting diode used in various display panels has a p-type compound semiconductor layer 12 and an n-type compound semiconductor layer 13 on one side of a p-type substrate 11. A rear surface electrode 14 formed of silver epoxy resin or the like is formed on the other surface side of the p-type substrate 11 and bonded to a lead frame, and a surface electrode on the surface of the n-type compound semiconductor layer 13 is wire-bonded. 15 are provided.

The shape of the surface electrode 15 is a circle or the like in order to improve the efficiency of extracting light to the outside, and the structure thereof differs depending on the type of crystal forming the lower compound semiconductor layer 13. For example, in a light emitting diode that emits red light, the compound semiconductor layer 13 is n-type GaAlAs, and therefore the surface electrode 15 is Au / Ni / AuGe / n-GaAlAs.
It has a multi-layer structure. Also, other crystals such as Ga
Au alloys are also used for the surface electrodes of compound semiconductors such as P and GaAsP.

[0004]

As described above, in the conventional light emitting diode, the surface electrode 15 is formed directly on the surface of the compound semiconductor layer 13, and the GaAlAs and GaP constituting this compound semiconductor layer are formed. , The crystal of GaAsP is fragile, so that it is easily cracked when a shock is applied by hitting the tip of the bonding capillary during wire bonding. In order to avoid this, the speed of wire bonding must be reduced, which is a cause of reduced production efficiency.

Further, conventionally, since an Au alloy is used as the material of the surface electrode, it is required to use Au for the bonding wire as well, which causes an increase in cost.

[0006]

In order to solve the above-mentioned problems, the present invention has a surface electrode provided for connecting to a bonding wire in a compound semiconductor optical device such as a light emitting diode and having a hole reaching the surface of a semiconductor crystal. An ohmic junction metal, an insulating buffer layer formed in a hole of the ohmic junction metal, and an Al / layer formed on the insulating buffer layer and having a peripheral edge joined to the ohmic junction metal.
It is composed of a bonding pad composed of a Mo multilayer film.

As compound semiconductors, GaAlAs and GaAs
s, GaP, GaAsP, GaN, ZnSe, GaAlAsP, I
nGaAsP or the like can be used, and the insulating buffer layer is SiO ₂ , Al ₂ O ₃ , PSG (Phospho Silicate Glass).
Etc. can be used, and the surface electrode is not limited to a circle, but can be a rectangle, a triangle, or the like.

[0008]

The light emission can be obtained by passing a current in the forward direction through the diode having the pn junction through the front electrode and the back electrode.

[0009]

1 to 6 are sectional views showing an example of a manufacturing process of a light emitting diode as a compound semiconductor optical device according to the present invention. The manufacturing procedure will be described below.

First, a p-type GaAs substrate (wafer) 1 having a thickness of 200 μm is formed on one surface of the p-type GaAs substrate 2 (wafer) by an epitaxial growth method so as to have a p-type GaAs layer 2 having a thickness of 50 μm (a mixed crystal ratio of the surface side is 0.
35) and an n-type GaAlAs layer 3 (mixed crystal ratio 0.65) having a thickness of 50 μm are formed, and red GaAlA having a wavelength of 660 nm is formed.
s Create an LED epitaxial wafer with a single heterostructure.

Next, as shown in FIG. 1, a back electrode 4 having a multi-layered structure of Au / AuZn / p-GaAs is formed on the back surface of the wafer by an evaporation method, and Au / Ni is formed on the surface of the n-type GaAlAs layer 3. A metal film 5 having a multi-layered structure of / AuGe / n-GaAlAs is formed, and the wafer is heated to impart ohmic characteristics to the electrodes 4 and the metal film 5. Then, as shown in FIG. 2, the metal film 5 is etched by photolithography into a ring-shaped ohmic contact metal 5 having an outer diameter of 150 μm and an inner diameter of 100 μm.

Next, as shown in FIG. 3, a 500 nm thick SiO ₂ layer 6 serving as an insulating buffer layer is formed on the surface of the n-type GaAlAs layer 3 including the ohmic contact metal 5, and thereafter, as shown in FIG. Then, only the SiO ₂ layer formed inside the ohmic contact metal 5 is left.

Further, as shown in FIG. 5, a multi-layered metal film 7 consisting of a Mo layer of 200 nm and an Al layer of 500 nm is formed on the surface of the n-type GaAlAs layer 3 including the ohmic junction metal 5 and the SiO ₂ layer 6. Then, after that, by leaving only a portion of the metal film that overlaps the ohmic contact metal 5 and the SiO ₂ layer 6 and dicing the wafer, as shown in FIG. 6, on the surface of the n-type GaAlAs layer 3, A surface electrode composed of a ring-shaped ohmic contact metal 5, a SiO ₂ layer 6 and a bonding pad 7 which covers the upper surfaces of the ohmic contact metal 5 and the SiO ₂ layer 6 and whose peripheral edge is connected to the ohmic contact metal 5 is formed. A light emitting diode is obtained.

In the light emitting diode thus obtained, the stress at the time of wire bonding is relaxed by the SiO ₂ layer 6, so that the cracks and chips of the GaAlAs crystal are reduced. Specifically, when wire bonding was performed on 10,000 chips, it was found that the light emitting diode of the conventional structure has
Although 0 chips were cracked, the number of cracks was 30 or less in the light emitting diode of the present invention. Further, since there are few cracks, the moving speed of the capillary tool at the time of wire bonding can be increased to about 1.5 times that of the conventional one, and as a result, the processing time per 10,000 pieces is from 6.1 hours to 5. I was able to reduce it to 5 hours.

[0015]

As described above, according to the present invention,
The surface electrode provided for connection with the bonding wire includes an annular ohmic contact metal, an insulating buffer layer formed inside the ohmic contact metal, and a peripheral edge of the insulating buffer layer formed on the insulating buffer layer. Since it is composed of a bonding pad that is bonded to the ohmic bonding metal, even if a shock is applied to the surface electrode portion during wire bonding, etc., this shock is absorbed by the buffer layer, so cracks and the like can be prevented, Since the wire bonding speed can be increased, the production efficiency is improved.

Further, the material of the surface electrode is not Au alloy but Al
The cost can be reduced by using the / Mo multilayer film.

[Brief description of drawings]

FIG. 1 is a sectional view showing a state in which an ohmic junction metal is formed in a manufacturing process of a compound semiconductor optical device (light emitting diode) according to the present invention.

FIG. 2 is a cross-sectional view showing a state where an ohmic junction metal is etched in a manufacturing process of a compound semiconductor optical device (light emitting diode) according to the present invention.

FIG. 3 is a sectional view showing a state in which an insulating buffer layer is formed in the manufacturing process of the compound semiconductor optical device (light emitting diode) according to the present invention.

FIG. 4 is a cross-sectional view showing a state where the insulating buffer layer is etched in the manufacturing process of the compound semiconductor optical device (light emitting diode) according to the present invention.

FIG. 5 is a cross-sectional view showing a state in which a metal film for a bonding pad is formed in the manufacturing process of the compound semiconductor optical device (light emitting diode) according to the present invention.

FIG. 6 is a sectional view of a compound semiconductor optical device (light emitting diode) according to the present invention.

FIG. 7 is a perspective view of a conventional light emitting diode.

[Explanation of symbols]

1 ... Substrate, 2 ... p-type GaAlAs layer, 3 ... n-type GaAlAs
Layer, 4 ... Back surface electrode, 5 ... Ohmic contact metal, 6 ... Buffer layer, 7 ... Bonding pad.

Claims (1)

[Claims] 1. A compound semiconductor device in which a front surface electrode and a back surface electrode are provided on a compound semiconductor chip having a pn junction, wherein the front surface electrode has an ohmic junction metal having a hole reaching a semiconductor crystal surface, and the ohmic junction metal has a hole. The insulating buffer layer is formed, and a bonding pad is formed on the insulating buffer layer and has a peripheral edge bonded to the ohmic contact metal, and the bonding pad is composed of an Al / Mo multilayer film. A compound semiconductor optical device characterized by the above.