JP3489395B2 - Semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device used in an optical device such as a light emitting diode or a laser diode, and more particularly to a structure of a semiconductor light emitting device having excellent light emitting characteristics and reliability.

[0002]

2. Description of the Related Art In recent years, the demand for high-power light-emitting devices made of III-V and II-VI compound semiconductors has increased, and materials for light-emitting devices operating in the short-wavelength visible region of blue or green or in the ultraviolet region. As a result, much attention has been focused on gallium nitride-based compound semiconductors. Among them, blue, green, violet and other light emitting diodes and laser diodes having a semiconductor light emitting element made of a gallium nitride compound semiconductor have been receiving attention.

A semiconductor light emitting element is generally made of a semiconductor crystal on a substrate by a metal organic chemical vapor deposition (hereinafter abbreviated as “MOCVD”) method, a molecular beam epitaxy method or the like.
A p-type layer and a p-type layer are sequentially stacked, and then A is formed on each layer.
It can be obtained by vapor-depositing an electrode material such as 1 or Au to take out the electrode, and separating the wafer into chips by dicing, scribing or the like.

However, in a light emitting device using a gallium nitride-based compound semiconductor as described above, since an insulating material called sapphire is generally used for the substrate,
It is very difficult to take out the electrodes from the upper surface and the lower surface of the device. Therefore, a part of the p-type layer is removed by etching to expose the n-type layer, and a metal such as Au or Ni is vapor-deposited in a circular or rectangular shape on the exposed n-type layer and p-type layer. ,
A configuration in which n-side and p-side electrodes are taken out from the upper surface side of the device is proposed in Japanese Utility Model No. 3027676.

In addition, since the p-type layer of gallium nitride-based compound semiconductor generally has a high resistance, even if the device current is injected from the p-side electrode electrically connected to the p-type layer, the p-type layer spreads sufficiently. Light is emitted only near the p-side electrode. Therefore, in this publication, a transparent electrode made of a metal such as Au or Ni is formed on almost the entire surface of the p-type layer, and the current applied to the electrode is spread over the entire surface of the p-type layer to emit light over the entire surface. Is proposed.

[0006] FIG. 10 (a) and 10 (b) is a top view and a sectional view showing a structure of a conventional semiconductor light emitting device using a gallium nitride-based compound semiconductor. 1 is a substrate, 2 is an n-type layer,
3 is a p-type layer, 4 is an n-side pad electrode, 5 is a p-side pad electrode, and 6 is a translucent electrode. The transparent electrode 6 is formed on almost the entire surface of the p-type layer 3. The p-side pad electrode 5 formed on the transparent electrode 6 and the n-side pad electrode 4 formed on the n-type layer are respectively formed. A gold wire (not shown) is connected.

In FIGS. 10 (a) and 10 (b),
The current injected into the p-side pad electrode 5 spreads over the entire surface by the transparent electrode 6 electrically connected to the p-side pad electrode 5,
It flows uniformly from the transparent electrode 6 to the p-type layer 3. This makes it possible to obtain uniform surface emission.

[0008]

However, the semiconductor light emitting device having such a structure has the following problems. That is, when the device size is reduced for the purpose of improving the manufacturing yield, since the p-side pad electrode and the n-side pad electrode are formed on the same surface side of the device, the p-side pad electrode and the n- side pad electrode are brought close to each other. Must be formed. Further, since the translucent electrode is generally formed by using a metal such as Au or Ni for electrically connecting to the p-type layer, it is necessary to form these metals very thin in order to make them translucent. However, if it becomes extremely thin, it becomes difficult for the current to flow uniformly in the plane of the transparent electrode. For this reason, the current injected from the pad electrode is less likely to spread over the entire surface of the transparent electrode, and the p- side pad electrode and n
The current easily concentrates in the region between the side pad electrodes. If the current is locally concentrated, it does not spread over the entire surface of the translucent electrode, and it is difficult to obtain uniform surface emission. Further, when the current is concentrated, local deterioration of the crystal and deterioration of the translucency of the translucent electrode due to migration of the electrode material from the pad electrode are likely to occur, resulting in a short device life.

An object of the present invention is to solve the above problems, and an object thereof is to provide a highly reliable semiconductor light emitting device which can obtain uniform surface emission even if the device size is small.

[0010]

In order to solve the above problems, a semiconductor light emitting device of the present invention comprises a substrate and a laminated structure in which an n-type layer and a p-type layer of a semiconductor are provided on the substrate. An etching removal portion is formed in which a part of the layer formed on the upper surface side of the p-type layer and the n-type layer is removed and a part of the layer formed on the substrate side is exposed. , A transparent electrode and a first pad electrode are electrically connected to the layer on the upper surface side, and a second pad electrode electrically connected to the layer formed on the substrate side is provided. The semiconductor light emitting device is provided on the surface of the etching removal portion, and the translucent electrode, the first pad electrode and the second pad electrode are formed on the same surface side, and this surface is the light emission observation surface side. A pad in which the first pad electrode and the second pad electrode of the translucent electrode face each other The thickness of the translucent electrode pole facing area,
From the thickness of the translucent electrode in the area other than the pad electrode facing area
It is also configured to be thin .

With this structure, it is possible to provide a highly reliable semiconductor light emitting device which can obtain uniform surface emission even if the device size is small.

[0012]

[0013]

[0014]

[0015]

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises a substrate, and a laminated structure in which an n-type layer and a p-type layer of a semiconductor are arranged on the substrate, A part of the layer formed on the upper surface side of the mold layer and the n-type layer is removed to form an etching-removed portion that exposes a part of the layer formed on the substrate side. The transparent electrode and the first pad electrode are electrically connected to each other, and the second pad electrode electrically connected to the layer formed on the substrate side is the etching removal portion. A semiconductor light-emitting device having a light-transmitting electrode, a first pad electrode, and a second pad electrode formed on the same surface side on the front surface, and this surface serving as the light emission observation surface side. the translucent electrode pad electrode facing region where the first pad electrode and the second pad electrode in the light of the electrode are opposed Saga, other than the pad electrode facing region
The semiconductor light emitting element is characterized in that it is thinner than the thickness of the transparent electrode in the region, and
The thickness of the translucent electrode depends on the pad electrode pair in the translucent electrode.
Being thinner than the thickness of the transparent electrode in the area other than the transparent area
The transparent electrode is applied to the area facing the pad electrode.
It has the effect of making it difficult for the flow to flow.

[0017]

[0018]

[0019]

[0020]

[0021] The invention described in claim 2 is the invention according to claim 1, wherein the p-type layer and the n-type layer is obtained by and each include a gallium nitride-based compound semiconductor, The gallium nitride-based compound semiconductor is included, and it has an effect of making it possible to uniform the surface emission on the light-emitting surface of the semiconductor light-emitting device including the gallium nitride-based compound semiconductor.

[0022]

[0023]

Specific examples of the embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a top view of a semiconductor light emitting device according to Embodiment 1 of the present invention. FIG. 2A is a line A in FIG.
It is sectional drawing along -A '. FIG. 2B shows a line BB '.
It is sectional drawing along. In these figures, 1 is a substrate, 2 is an n-type layer, 3 is a p-type layer, 4 is an n-side pad electrode, 5
Is a p-side pad electrode, and 6 is a translucent electrode. The transparent electrode 6 is formed on almost the entire surface of the p-type layer 3, and includes a pad electrode facing region 6a where the p-side pad electrode 5 and the n-side pad electrode 4 face each other and a region 6b other than the pad electrode facing region. Become.

As shown in the sectional view of FIG. 2B, the pad electrode facing region 6a of the translucent electrode 6 and the region 6b other than the pad electrode facing region are formed to have different thicknesses. In the embodiment, the pad electrode facing region 6a
Is formed to be thinner than the thickness of the region 6b other than the region facing the pad electrode. By forming the translucent electrode 6 with such a configuration, it becomes difficult for the current to flow in the pad electrode facing region 6a where the current easily concentrates, and the region 6b other than the pad electrode facing region where the current relatively easily flows.
The electric current spreads. Therefore, the current spreads over the entire transparent electrode 6 and flows evenly over the entire p-type layer 3, whereby uniform surface emission is obtained.

3 to 6 are a top view and a cross-sectional view for explaining each step of the method for manufacturing a semiconductor light emitting device according to the first embodiment of the present invention. In each drawing, the cross-sectional view shows a cross-section taken along the line AA ′ in the top view.

First, the thickness of sapphire is about 100 μm.
4 μm thick n-type layer 2 made of a gallium nitride-based compound semiconductor and a thickness of 0.
P-type layer 3 made of 4 μm gallium nitride-based compound semiconductor
Grow in order. The top view and the cross-sectional view are respectively shown in FIG.
Shown in (a) and FIG. 3 (b).

Next, Ni and Au are vapor-deposited on the p-type layer 3 to a thickness of 2 nm and 5 nm, respectively, using an electron beam evaporation method. A metal mask having a shape capable of covering the p- side pad electrode 5, the n- side pad electrode 4, and the pad electrode facing region 6a of the translucent electrode is arranged on the p-type layer 3, and Au is further formed with a thickness of 5 nm. Vapor deposition. Next, a photoresist is formed on the transparent electrode 6 by photolithography,
After exposure and patterning, the transparent electrode 6 is patterned into a shape similar to that of the photoresist by etching. The wafer on which the transparent electrode 6 has been patterned is immersed in a solvent to remove the photoresist.
A top view and a cross-sectional view thereof are shown in FIGS. 4 (a) and 4 (b), respectively.
Shown in. The metal mask used for vapor deposition may have any shape as long as it can cover the pad electrode facing region 6a of the p- side pad electrode 5, the n- side pad electrode 4, and the translucent electrode 6, and for example, The shape shown by the shaded portion in FIG.

Next, the p-type layer 3 is formed by using the plasma CVD method.
And a silicon dioxide film as a protective film on the transparent electrode 6
It is formed to a thickness of μm, a photoresist is formed by photolithography, exposure is performed, and patterning is performed. Further, the wafer is dipped in hydrofluoric acid, and the silicon dioxide film is etched and patterned into a shape similar to that of the photoresist. After the wafer is washed with water, it is immersed in a solvent to remove the photoresist. Using the silicon dioxide film patterned in this way as a mask, the p-type layer 3 whose upper surface is exposed is dry-etched to form the n-type layer 2.
Expose part of. Then, the remaining silicon dioxide film is removed by immersing it in the hydrofluoric acid solution. The top view and the cross-sectional view are shown in FIG.
It shows in (b).

An n-side pad electrode 4 made of Al is formed on the exposed n-type layer 2, and a p-layer made of Au is formed on the transparent electrode 6.
The side pad electrodes 5 are respectively formed by the electron beam evaporation method. In this way, the semiconductor light emitting device as shown in FIGS. 6A and 6B is completed.

(Comparative Example 1) In the step of forming the translucent electrode in the method for manufacturing a semiconductor light emitting device according to the first embodiment, Ni and Au are respectively deposited on the p-type layer 3 by using the electron beam evaporation method. A semiconductor light emitting device having a conventional structure is manufactured in the same manner as in the first embodiment except that vapor deposition is performed without using the metal mask described above with a thickness of 2 nm and 5 nm. The sample thus obtained was designated as Comparative Example 1.

Next, the semiconductor light emitting device manufactured by the above manufacturing method was evaluated. As an evaluation, a near-field pattern in a light emitting state when driven with a forward current of 10 mA and an energization life test of 1000 hours when driven with a forward current of 20 mA were performed . The near field pattern is p, as shown by line BB 'in FIG.
The measurement was performed along a diagonal line different from the diagonal line connecting the side pad electrode 5 and the n-side pad electrode 4.

7A and 7B show a near field pattern and a sectional view of the semiconductor light emitting device according to the first embodiment, respectively. As can be seen from these figures, the current does not concentrate in the pad electrode facing region of the translucent electrode where the current tends to concentrate, and the current spreads over the entire translucent electrode.
A current flows uniformly through the p-type layer, and uniform surface emission is obtained. This light-emitting element showed almost no deterioration in luminance even after conducting an energization life test for 1000 hours. Furthermore, no change was observed in the translucent electrode. On the other hand, in the semiconductor light emitting device having the conventional structure manufactured by the method of Comparative Example 1, as shown in the near field pattern and the cross-sectional view shown in FIGS. Since current is likely to concentrate in the pad electrode facing region of the electrode, uniform surface emission cannot be obtained. After conducting the energization life test for 1000 hours, the luminance decreased to 40% of the initial value of energization. Further, discoloration was observed in the region of the translucent electrode facing the pad electrode, and it was confirmed that the translucency of the translucent electrode was lowered.

(Embodiment 2) In the step of forming a translucent electrode in the method for manufacturing a semiconductor light emitting device of Embodiment 1 described above, Ni and Au are deposited on the p-type layer 3 by using an electron beam evaporation method.
Of the silicon dioxide film patterned by photolithography as a mask instead of the metal mask when depositing each of 2 nm and 5 nm in thickness, and the silicon dioxide film used as the mask is removed after vapor deposition. A semiconductor light emitting device of the second embodiment is manufactured in the same manner as the first embodiment except that the vapor deposition is performed with the thickness of.

FIG. 9A is a top view of the semiconductor light emitting device according to the second embodiment of the present invention, and FIG. 9B is a sectional view taken along the line BB '. As can be seen from FIG. 9B, a substantially rectangular step is formed at the boundary between the pad electrode facing region 6a of the translucent electrode 6 and the region 6b other than the pad electrode facing region to change the film thickness. There is.

Similar to the semiconductor light emitting device of the first embodiment,
When the semiconductor light emitting device of the second embodiment is evaluated,
From the near-field pattern, it was confirmed that the current spreads almost uniformly within the transparent electrode surface. Also, in the energization life test, there was almost no deterioration in brightness, and no change was observed in the translucency of the translucent electrode.

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

As described above, according to the present invention, it is possible to obtain a highly reliable semiconductor light emitting device which can obtain uniform surface emission even if the device size is small. .

[Brief description of drawings]

FIG. 1 is a top view showing a structure of a semiconductor light emitting device according to a first embodiment of the present invention.

FIG. 2A is a sectional view taken along the line AA ′ of the semiconductor light emitting device according to the first embodiment of the present invention, and FIG. 2B is a sectional view of the semiconductor light emitting device according to the first embodiment of the present invention.
-B 'sectional view

FIG. 3A is a top view for explaining the method for manufacturing the semiconductor light emitting element according to the first embodiment of the present invention. FIG. 3B shows the method for manufacturing the semiconductor light emitting element according to the first embodiment of the present invention. Cross section for

4A is a top view for explaining the method for manufacturing the semiconductor light emitting device according to the first embodiment of the present invention. FIG. 4B is a view for explaining the method for manufacturing the semiconductor light emitting device according to the first embodiment of the present invention. Cross section for

FIG. 5A is a top view for explaining the method for manufacturing the semiconductor light emitting element according to the first embodiment of the present invention. FIG. 5B shows the method for manufacturing the semiconductor light emitting element according to the first embodiment of the present invention. Cross section for

FIG. 6A is a top view for explaining the method for manufacturing the semiconductor light emitting element according to the first embodiment of the present invention. FIG. 6B shows the method for manufacturing the semiconductor light emitting element according to the first embodiment of the present invention. Cross section for

7A is a diagram showing a near-field pattern of the semiconductor light emitting device according to the first embodiment of the present invention. FIG. 7B is a sectional view of the semiconductor light emitting device according to the first embodiment of the present invention.

FIG. 8A is a diagram showing a near-field pattern of a conventional semiconductor light emitting device, and FIG. 8B is a sectional view of the conventional semiconductor light emitting device.

9A is a top view showing a structure of a semiconductor light emitting element according to a second embodiment of the present invention, and FIG. 9B is a sectional view showing a structure of a semiconductor light emitting element according to the second embodiment of the present invention.

FIG. 10 (a) shows the structure of a conventional semiconductor light emitting device.
Plan view (b) Sectional view showing the structure of a conventional semiconductor light emitting device

[Explanation of symbols]

1 substrate 2 n-type layer 3 p-type layer 4 n side pad electrode 5 p-side pad electrode 6 Translucent electrode 6a Pad electrode facing area 6b Area other than pad electrode facing area

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Claims (2)

(57) [Claims] 1. A substrate, and a laminated structure in which a semiconductor n-type layer and a p-type layer are provided on the substrate, and the substrate is formed on the upper surface side of the p-type layer and the n-type layer. Part of the layer formed on the substrate side is exposed to form an etching-removed portion, and the translucent electrode and the first pad electrode are formed on the layer on the upper surface side. A second pad electrode that is electrically connected and is electrically connected to the layer formed on the substrate side is provided on the surface of the etching-removed portion, and the transparent electrode and the first electrode are provided. A semiconductor light emitting device in which a pad electrode and a second pad electrode are formed on the same surface side, and this surface is a light emission observation surface side, and the first pad electrode and the second pad in the translucent electrode The thickness of the translucent electrode in the pad electrode facing area facing the electrode is the pad electrode facing
A semiconductor light-emitting device characterized by being thinner than the thickness of the translucent electrode in a region other than the region . 2. The p-type layer and the n-type layer are nitrided, respectively.
A gallium compound semiconductor is included.
1. The semiconductor light emitting device according to 1 .