JPH07221347A - Gallium nitride compound semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To reduce the chip size of a gallium nitride compound semiconductor light emitting element and prevent short-circuits between its positive and negative electrodes so as to secure the light emitting efficiency of the element by removing a sapphire substrate on the side opposite to the side where gallium nitride compound semiconductor layers are laminated and forming one electrode on the semiconductor layer exposed on the removed part. CONSTITUTION:After successively forming an n-type layer 2 and p-type layer 3 on a sapphire substrate 1, a positive electrode 12 is formed on the entire surface of the layer 3. Then the half of the surface of the sapphire substrate where no gallium nitride compound semiconductor layer is laminated is cut off in a prescribed shape. After cutting, the substrate 1 is etched until the etched depth reaches the layer 2 and the layer 2 is exposed. After the layer 2 is exposed, negative electrodes 11 composed of Ti and Al are formed on the layer 2. Thereafter, a light emitting element is obtained by cutting the substrate into chips having a desired shape. Therefore, the electrodes do not come into contact with each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium nitride-based compound semiconductor (In _X Al _Y Ga _1-XY N, _0≤X≤1 , used for blue to green light emitting diodes, laser diodes, etc.
The present invention relates to a light emitting device having 0 ≦ Y ≦ 1), and particularly to a light emitting device having a gallium nitride compound semiconductor layer laminated on the surface of a sapphire substrate.

[0002]

2. Description of the Related Art As shown in FIG. 1, a light emitting device made of a gallium nitride-based compound semiconductor basically has an n-type gallium nitride-based compound semiconductor layer (hereinafter referred to as an n-type layer) on the surface of a sapphire substrate. 2 and a p-type gallium nitride compound semiconductor layer (hereinafter referred to as p-type layer) are laminated. As described above, in the gallium nitride-based compound semiconductor light emitting device, since the gallium nitride-based compound semiconductor is laminated on the surface of the insulating sapphire substrate, the negative electrode 11 formed in the n-type layer 2 and the p-type layer 3 are formed. Formed positive electrode 1
In reality, 2 is unavoidably formed on the same side.

[0003]

The light emitting device having both positive and negative electrodes on the same surface has the following problems.
First of all, compared to other light emitting devices that can form electrodes on the substrate side, the chip size is large, so the number of chips that can be cut out from one wafer is small, and the manufacturing cost per chip is high. . Secondly, when the chip size is reduced, the distance between the positive electrode and the negative electrode is inevitably narrowed, and one electrode may come into contact with the other electrode and electrically short-circuit. Thirdly, since it is necessary to remove a part of the p-type layer 3 to expose the n-type layer 2 in an area where an electrode can be formed, the area of the pn junction interface is reduced and the light emitting area is reduced. To do.

In the gallium nitride-based compound semiconductor light emitting device using sapphire as a substrate, all the above problems can be solved if the electrodes can be taken out from the substrate side as is the case with other semiconductor light emitting devices. Therefore, an object of the present invention is to provide a gallium nitride-based compound semiconductor light emitting device that can solve all of the above three problems.

[0005]

A gallium nitride-based compound semiconductor light-emitting device according to the present invention has a gallium nitride-based compound semiconductor layer laminated on one surface of a sapphire substrate, and the gallium nitride-based compound semiconductor layer has a pair of positive and negative electrodes. In a gallium nitride-based compound semiconductor light-emitting device having electrodes, a part of the sapphire substrate is a gallium nitride-based compound semiconductor layer from the other sapphire substrate surface facing the surface on which the gallium nitride-based compound semiconductor layer is laminated. Of the gallium nitride-based compound semiconductor layer to expose the gallium nitride-based compound semiconductor layer, and a positive electrode or a negative electrode is formed on the exposed surface of the gallium nitride-based compound semiconductor layer.

[0006]

2 is a sectional view showing the structure of a light emitting device according to an embodiment of the present invention, and the same reference numerals as those in FIG. 1 denote the same members. In this figure, a part of the sapphire substrate 1 is removed by etching from the surface of the sapphire substrate 1 facing the side on which the gallium nitride-based compound semiconductor is laminated, and the n-type layer laminated on the other sapphire substrate surface 1 is shown. By exposing and forming the negative electrode 11 on the exposed n-type layer 2, the positive electrode 12 and the negative electrode 11 are opposed to each other with the pn junction interface therebetween. Thus, when electrodes are formed on the exposed semiconductor layer by removing a part of the substrate, the electrodes are opposed to each other with the gallium nitride-based compound semiconductor layer interposed therebetween. Since it is not necessary to form only one kind of electrode in the device, the chip size of the light emitting element can be reduced, and the pn junction interface is not damaged and the area thereof is not reduced, so that the luminous efficiency is reduced. There is no.

FIG. 3 is a sectional view showing the structure of a light emitting device of another embodiment of the present invention. This light emitting device has a structure in which the sapphire substrate 1 on both sides of the chip is removed to expose the n-type layer 2 and two negative electrodes 11 are formed on the surface of the n-type layer. It goes without saying that this element also has the same operation as the element shown in FIG.

[0008]

FIG. 4 is a sectional view showing the structure of a wafer obtained in each step of the embodiment, and the embodiment will be described with reference to this drawing.

A wafer is prepared in which an n-type layer 2 and a p-type layer 3 are sequentially stacked on a 2-inch φ sapphire substrate 1. First, a positive electrode 12 made of Ni and Au is formed on the entire surface of the p-type layer 3.
To form. The positive electrode 12 can be formed by using, for example, vapor deposition spatter.

Next, as shown in FIG. 4A, the surface of the sapphire substrate on which the gallium nitride compound semiconductor layer is not laminated is half-cut in a predetermined shape. As the means for half-cutting, for example, a method of physically cutting using a dicer, a method of physically or chemically cutting by etching, or the like can be used. Although either dry etching or wet etching may be used for the etching, it goes without saying that a mask having a predetermined shape is formed on the surface of the sapphire substrate 1 by using a photolithography technique before the etching.

After the half-cut, as shown in FIG. 4B, etching is performed until the cut depth reaches the n-type layer 2 and the n-type layer 2 is exposed on the surface. It is difficult to control the depth by other methods unless this step is necessarily performed by etching. When the sapphire substrate is removed by etching from the beginning in the step A, this step can be continuously performed. However, if a part of the sapphire substrate 1 is removed in advance by a dicer or the like and half-cutting is performed, the etching can be performed faster than the etching from the beginning. During the etching of the sapphire substrate 1, p
Since the entire surface of the mold layer 3 is formed as the positive electrode 12 in advance, there is an advantage that the thinned gallium nitride compound semiconductor layer is less likely to be cracked during the formation of the negative electrode 11. As described above, it is a preferable means to form a full-scale electrode on the uppermost layer of the gallium nitride-based compound semiconductor layer before removing a part of the sapphire substrate 1.

After the n-type layer 2 is exposed on the surface, a negative electrode 11 made of Ti and Al is formed on the n-type layer 2 as shown in FIG. 4C. Similarly to the positive electrode, the negative electrode 11 can also be formed using a technique such as vapor deposition or sputtering.

After forming the negative electrode 11, the light emitting device of the present invention is obtained by cutting into a desired chip shape as shown in D of FIG. The device thus obtained had a cross-sectional shape as shown in FIG. 3, and it was possible to produce a chip with a size of 200 μm square. Further, since there is no short circuit between the electrodes, the reliability of the device was very excellent.

On the other hand, etching was performed from the surface on which the gallium nitride-based compound semiconductor layer was laminated, and electrodes were formed on the exposed n-type layer 2 and p-type layer 3 on the same surface side, respectively. One chip size was obtained. Is required to be 350 μm square at the minimum, and the balls formed during bonding come into contact with other layers to cause a short circuit.

[0015]

As described above, in the gallium nitride-based compound semiconductor light-emitting device of the present invention, the sapphire substrate on the side opposite to the side on which the gallium nitride-based compound semiconductor layer is laminated is removed, and the exposed portion is exposed. Since one electrode is formed on the gallium nitride-based compound semiconductor layer described above, the other electrode is naturally opposed to the other electrode, and the electrodes do not come into contact with each other at all, which is very excellent in reliability. Further, since only one electrode is required for one surface, the chip size can be reduced to the minimum size capable of forming one electrode, thus improving the productivity.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of a conventional gallium nitride-based compound semiconductor light emitting device.

FIG. 2 is a schematic cross-sectional view showing one structure of a gallium nitride-based compound semiconductor light emitting device of the present invention.

FIG. 3 is a schematic cross-sectional view showing one structure of a gallium nitride-based compound semiconductor light emitting device of the present invention.

FIG. 4 is a schematic cross-sectional view showing the structure of a gallium nitride-based compound semiconductor wafer obtained in the process of the example of the present invention.

[Explanation of symbols]

 1 ... Sapphire substrate 2 ... N-type layer 3 ... P-type layer 11 ... Negative electrode 12 ... Positive electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Nakamura 491, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture Nichia Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A gallium nitride compound semiconductor light-emitting device comprising a gallium nitride compound semiconductor layer laminated on one surface of a sapphire substrate, and a pair of positive and negative electrodes formed on the gallium nitride compound semiconductor layer. From the sapphire substrate surface facing the surface on which the gallium nitride compound semiconductor layer is laminated, a part of the sapphire substrate is removed at a depth reaching the gallium nitride compound semiconductor layer, the gallium nitride compound semiconductor layer is exposed, A gallium nitride-based compound semiconductor light-emitting device comprising a positive or negative electrode formed on the exposed surface of the gallium nitride-based compound semiconductor layer.