JPS6034827B2 - Gallium phosphide light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a light emitting device made of gallium phosphide, which is one of compound semiconductors, and a manufacturing method thereof, and more particularly to a gallium phosphide light emitting device with an improved electrode structure and a manufacturing method thereof.

Among compound semiconductors, gallium phosphide (Gap) is often used in light emitting diodes.

This GaP light emitting diode is attracting attention because it can freely emit red to green light by adding impurities. For example, this configuration is shown in FIG. That is, a p-type gap layer 12 is provided on an n-type GaP substrate 11 to form a p-n junction 13, and electrodes 1 are provided on both sides of the beret.
1a and 12a are provided and mounted on a header 14 via a conductive paste 15 with the n-type gap substrate 11 side facing down. In addition, there is a terminal 1 for taking out the electrode on the bottom 14.
1c and 12c are taken out and attached to the terminal 12c by a lead wire 12b from the electrode 12a of the p-type Gap layer. Naturally, the electrode 11a and the terminal 12c of the n-type GaP layer substrate are electrically connected. Matahetsuda 14
The upper part of is covered with epoxy resin 16. By the way, in the configuration of FIG. 1, the electrode 12a to the p-type Gap layer is in ohmic contact with the p-type GaP layer, and the smaller the contact resistance is, the better.

- Lead wire 12b can be easily bonded. ■Do not reduce luminous efficiency. (2) Must be able to withstand strong acid etching solution used in the treatment process for the 13th surface after p-n to improve luminous efficiency. ■Performance such as the ability to perform fine etching of electrode films is required. No metal film has been found that satisfies all of these conditions, and the reality is that metal films are manufactured that are unsatisfactory with one or two of the above conditions.

That is, 1 to 2 mainly composed of Au as a metal that satisfies (■).
Wt% technology or Zn alloy film is known. However, it is possible under the conditions that this gold film satisfies ■, but does not satisfy ■ and ■. In order to explain this reason, the process from electrode film formation to pellet format is shown in FIGS. 2a to 2e. In FIG. 2, an n-type GaP layer 22 and a p-type GaP layer 23 are formed on a wafer 21 to form an n-type GaP wafer.
A substrate having an electrode surface 24 formed on its surface 21 is prepared.

Then, on the p-type gap layer 23, the above-mentioned Au-Be or Au
- A Zn alloy film 24 is formed by vacuum evaporation (FIG. 2a). Next, using photoresist, the double-sided electrode film 24,
25 is finely processed by chemical etching. Then, the photoresist was removed, and the
Each electrode film is heated for about 00010 minutes to form a p-type GaP layer 23.
And make ohmic contact with the n-type Gap wafer 21 (FIG. 2b). Next, it is processed and separated into pellets of predetermined dimensions using a dicing, scribing method, etc. (FIG. 2c). At this time, due to machining, the side surface of the p-n junction, which becomes the light emitting part, is crushed and the light emitting efficiency deteriorates. To restore this, the fractured layer must be removed by etching. Also, in the etching, it is desirable that the entire exposed GaP surface other than the electrodes be finished in a rough surface with unevenness rather than a smooth surface. An etching solution that satisfies both of these requirements is a heated solution of hydrochloric acid and sulfuric acid. Through this process, a light emitting device pellet as shown in FIG. 2d is completed. After this, as mentioned above, To-Betsuda 26
Then, the electrode 24 on the n-type GaP layer side is adhesively fixed with a conductive paste 27, and the gold wire 28 is bonded to the P-side electrode 25 (FIG. 2e). Although the above is a normal process, the above-mentioned disadvantages occur in this case.

That is, it is certain that ohmic contact can be made by heat treatment of the Au layer or AuZn alloy film on the surface of the p-type gap layer, but conversely, heat treatment can also cause Ga on the surface of the electrode film.
and P ions permeate the film and are deposited, and the oxidation of Be or Zn elements also overlaps, forming a complex oxide film of Ga--P--Be(-Zu)--. As a result, the adhesion of the bond becomes extremely poor, and in some cases, the bonding is not possible at all, but usually one bonding is not successful and the bonding operation is repeated 4 to 5 times to remove the oxide film on the surface. Once you scrape it off, you will be able to bond for the first time. In addition, since the diffusion coefficient of Ga element into Au is large, a large amount of Ga element is deposited on the electrode film surface. For this reason, the amount of Ga in the GaP crystal itself is drastically reduced, resulting in failure of the crystal, and the luminous efficiency is lower than the theoretical value. Furthermore, in the case of a special alloy like Ship A e, it is difficult to microfabricate and uniformly etch, resulting in a decrease in beret yield. On the other hand, if an attempt is made to eliminate the residual film by elongating the etching time, for example, a good film will be over-etched in a far-etched area, resulting in an unusable product. Note that the alloy film mainly composed of Au is
It has the advantage of being resistant to the strong acids used to create the frost effect.

Therefore, the present invention solves the above-mentioned problems and provides a Gap light-emitting element with a novel electrode structure using a material that is resistant to strong acids and a method for manufacturing the same.

An embodiment of the present invention will be described below with reference to FIGS. 3a to 3d.

First, Figure 3a shows the n-type Ga of the GaP substrate that forms the p-n junction.
This is a state in which an electrode film 31 of a microfabricated n-type GaP wafer is attached to the surface of the p-wafer 21.

As shown in FIG. 3b, a metal mask 3 is placed on the p-type Gap layer surface.
2 is placed, and a three-layer electrode film is formed according to the shape of the mask 32 by, for example, sputtering in a vacuum. These three layers are successively deposited in the order of gold-beryllium (Au-Mo) alloy film 33, tantalum (Ta) film 34, and gold (Au) film 35. .1mm,
Ta film: 0.2 to 0.4 m, Au film: 0.2 to 1 m
It is. Then, 50 min.
Heat treatment was performed for 10:00 and 10 minutes, and the subsequent steps were the same as those in FIG. 2c described above. Formation of a three-layer film using this mask eliminates all of the above-mentioned drawbacks.

In other words, it can be used as a mask for alloy films that are difficult to etch, such as Au-Mo alloy films. The use of a Ta film allows for better patterning and no etching, resulting in G resistance even when heated to 500°C.
Based on this experimental discovery that the Ta film absorbs the movement of a, P; Be elements, no oxide layer was observed on the Au surface.
Bonding can now be done in one go with 100% probability, the thickness of the Au film is 1/5 to 1/10 of the conventional film, so there is no decrease in luminous efficiency, and the Ta film can be bonded with hydrochloric acid or nitric acid. It was found that it was not affected by the heated liquid and could sufficiently withstand the frost effect process. In addition, instead of Ta film, tungsten (W) film, niobium (Nb) film, silconium (
We also experimented with Zr) film, molybdenum (Mo) film, nickel (Ni) film, etc. We found that the absorption rates of Ga, P, and Be elements are different and depend on the thickness of each film, but the Zr film was attacked by hydrochloric acid heat treatment, the Mo and Ni films were attacked by hydrochloric acid heat treatment, and the Au film was attacked by hydrochloric acid heat treatment. It was discovered that the bonding was impossible due to peeling. It was confirmed that the W film and the Nb film have the same effect as the Ta film. The same experiment was conducted using an Au-Zn alloy film instead of the Au-myo film.

It has been found that Ta, W, and Nb films have the same effect in this case as well. Furthermore, it has been found that the Au-Zn film can be easily etched with an Au etchant, so there is no need to form a three-layer film using a mask. In this case, the three-layer etching solution is to first remove the Au film with an Au etching solution such as iodine-
(12) The Ta film is etched with an alkaline etching solution such as caustic soda (NaO) using a mixture of potassium iodide (KI) and potassium iodide (KI).
The Au--Zn film may be etched using the same Au etching solution as described above, using a solution containing 1 H of potassium potassium (KOH) as a main component. However, if the formed film is etched, it will easily peel off from the Au-Zn film because the adhesive strength of the Au-Zn film is weak. Therefore, immediately after film formation,
It is preferable to carry out etching after heat treatment is performed to diffuse Zn and establish ohmic contact. However, in mass production processes, eliminating the etching process saves labor, reduces time, improves yield, and reduces costs.

Therefore, it is best to form using a mask. Furthermore, by using the Ta film, 100% bonding can be achieved in one time as described above, and the time loss during bonding can be reduced to zero. Of course, it can withstand the frost effect process without reducing the luminous efficiency, so the effective luminous efficiency can be increased to 100%.
% Gap light emitting element is obtained.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a light emitting diode used to explain the electrodes of a conventional GaP light emitting device, and Figures 2 a to e are a conventional method for forming an electrode film of a p-type GaP layer and the steps of a pellet process. Cross-sectional views, FIGS. 3a to 3d, show p-type G according to the present invention.
It is a figure which shows the manufacturing process and structure of the electrode film of an ap layer. 31 is an n-type Gap wafer electrode film, 32 is a metal mask, 33 is an Au-Be alloy film, 34 is a tantalum film, 35 is a gold film, and 36 is a pellet. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. In a gallium phosphide light-emitting device having a p-n junction, the electrode of the p-type layer constituting the p-n junction is made of at least one metal such as an alloy layer of beryllium or zinc mainly composed of gold, tantalum, or niobium. A gallium phosphide light emitting device characterized in that it is constructed by sequentially laminating layers and gold.