JP2748818B2 - Gallium nitride based compound 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 the general formula In _x Al _Y Ga
_{The present invention} relates to a gallium nitride-based compound semiconductor light emitting device including a gallium nitride-based compound semiconductor represented by _1-XYN (0 ≦ X <1, 0 ≦ Y <1).

[0002]

2. Description of the Related Art Recently, GaN, GaAlN, InGaN,
A light-emitting element using a gallium nitride-based compound semiconductor such as InAlGaN has attracted attention. The gallium nitride-based compound semiconductor is generally grown on a sapphire substrate. A light emitting element using an insulating substrate such as sapphire, unlike other light emitting elements using a semiconductor substrate such as GaAs or GaAlP, cannot take out an electrode from the substrate side. A pair of positive and negative electrodes provided on the semiconductor layer are formed on the same surface side. In particular, in the case of a gallium nitride-based compound semiconductor light-emitting device, since sapphire is translucent, the sapphire substrate side is often used as a light-emission observation surface with the electrode surface facing down (JP-A-4-106).
70, JP-A-4-10671.

On the other hand, a gallium nitride-based compound semiconductor light emitting device having a structure in which a sapphire substrate side is wire-bonded from above to respective electrodes provided on the same surface side is also known (JP-A-60-175468). No.
JP-A-61-56474).

[0004]

A light emitting element having a structure in which the sapphire substrate side has a light emission observation surface has an advantage that light emission can be observed from the entire substrate side without being hindered by the electrodes. Since it is difficult to reduce the interval between the lead frames connecting the two electrodes, the chip size is increased to about 1 mm or more, and there is a disadvantage that the number of chips per wafer is reduced.

On the other hand, a light emitting device having a structure in which the sapphire substrate side faces down has an advantage that the chip size can be reduced, but is formed on a gallium nitride-based compound semiconductor layer (particularly, the uppermost p-type layer). There is a disadvantage in that light emission is blocked by the electrode and luminous efficiency is reduced. That is, when wire bonding a gold wire or the like to the electrode, the electrode area at the bonding position requires a certain size according to the thickness of the gold wire, so if the position is in the center of the light emitting surface, For example, light emission is blocked by a central electrode, a ball formed during wire bonding, or the like.

Accordingly, the present invention has been made to solve the above two problems, and a first object is to reduce the size of a gallium nitride-based compound semiconductor light emitting device.
A second object is to improve the luminous efficiency by taking out light emitted from a small-sized light emitting element to the outside without interrupting as much as possible.

[0007]

According to a method of manufacturing a gallium nitride-based compound semiconductor light emitting device of the present invention, an n-type gallium nitride-based compound semiconductor layer and a p-type gallium nitride-based compound semiconductor layer are provided on a substrate. A p-electrode is formed on the surface of the gallium nitride-based compound semiconductor layer, and an n-electrode is formed on the exposed surface of the n-type gallium nitride-based compound semiconductor layer after a part of the p-type gallium nitride-based compound semiconductor layer is removed. By energizing the p-electrode and the n-electrode on the same side,
In the method of manufacturing a gallium nitride-based compound semiconductor light-emitting device that observes light emission from the electrode side, the step of forming the p-electrode includes forming a metal thin film on a surface of a p-type gallium nitride-based compound semiconductor layer constituting each chip. Forming a translucent electrode for ohmic; and forming a pedestal electrode for wire bonding on a part of the surface of the translucent electrode at a position diagonal to the n-electrode. In the step of forming an electrode, a part of the p-type gallium nitride-based compound semiconductor layer at a position diagonal to the pedestal electrode is removed by etching to expose the surface of the underlying n-type gallium nitride-based compound semiconductor layer. Forming a wire bonding electrode on the exposed portion. In the step of forming the p-electrode, a gap is formed between the diagonally arranged n-electrode and the pedestal electrode. The light-transmissive electrode is formed on substantially the entire surface of the p-type gallium nitride-based compound semiconductor layer serving as a light emission observation surface, and the p-type nitride under the light-transmitting electrode is formed when the n-electrode and the pedestal electrode are energized. The present invention is characterized in that a current is uniformly spread over the gallium-based compound semiconductor layer so that substantially uniform light emission is observed from the translucent electrode. Preferably, the method for manufacturing a nitride semiconductor light emitting device includes a step of forming the light-transmitting electrode and then annealing the wafer on which the electrode is formed. Further, a gallium nitride-based compound semiconductor light emitting device according to the present invention has an n-type gallium nitride-based compound semiconductor layer and a p-type gallium nitride-based compound semiconductor layer on a substrate, and has a surface of the p-type gallium nitride-based compound semiconductor layer. An n-electrode is formed on the surface of the n-type gallium nitride-based compound semiconductor layer exposed by removing a part of the p-type gallium nitride-based compound semiconductor layer, and the p-electrode and the n-electrode are flush with each other. In the gallium nitride-based compound semiconductor light emitting device formed on the side, the p-electrode is a pedestal electrode for wire bonding formed at a part of one corner of a substantially rectangular p-type gallium nitride-based compound semiconductor layer. And a metal thin film for current spreading and ohmic having a larger area than the pedestal electrode formed under the pedestal electrode in contact with the p-type gallium nitride-based compound semiconductor. Consists of a transparent electrode, the n-electrode, forms a substantially rectangular n
A p-type gallium nitride-based compound semiconductor layer formed by etching on a surface of an n-type gallium nitride-based compound semiconductor layer at a position diagonal to the pedestal electrode in the n-type gallium nitride-based compound semiconductor layer; Wherein the translucent electrode is located between the pedestal electrode and the n-electrode at diagonal positions, and substantially over the entire surface of the p-type gallium nitride-based compound semiconductor layer serving as a light emission observation surface;
It is characterized by having a light-emitting surface on which a current is uniformly spread to the p-type gallium nitride-based compound semiconductor layer below the translucent electrode by conducting electricity between the pedestal electrode and the n-electrode, and a substantially uniform light emission is observed. .

A gallium nitride-based compound semiconductor light emitting device (hereinafter referred to as a light emitting device) of the present invention will be described with reference to FIGS. FIG. 1 is a plan view of a light emitting device according to one embodiment of the present invention as viewed from the gallium nitride-based compound semiconductor layer side, and FIG. 2 is a cross-sectional view of the light emitting device of FIG. It is an outline sectional view. This light-emitting element has a structure in which an n-type layer 2 and a p-type layer 3 are sequentially stacked on a sapphire substrate 1, and a part of the p-type layer 3 is etched to form n
The electrode layer 4 is exposed on the n-type layer 2 by exposing the mold layer 2.
A linear electrode 5 is formed thereon. Further, the electrodes 5 formed on the p-type layer are linearly formed so as not to hinder light emission as much as possible, and a plurality of electrodes 5 are provided on the p-type layer 3 so as to spread the current uniformly.

The gold wire 7 is wire-bonded to the electrode 4 and the electrode 5 of the light emitting element as described above to connect the lead frame and the gold wire 7, thereby completing the light emitting element. Reference numeral 6 denotes a ball formed from the gold wire 7 during wire bonding. In the light emitting device of the present invention, as shown in FIG. 1, a corner of the p-type layer 3 is etched to form an electrode 4 at a corner of the n-type layer 2, and the electrode 4 is wire-bonded. Further, the wire bonding position of the electrode 5 is defined as a corner of the p-type layer 3. As shown in these figures, the area of the p-type layer 3 can be increased by wire-bonding the electrode 4 as a corner of the n-type layer 2, and light emission can be obtained in a wide area. Furthermore, by setting the wire bonding position of the electrode 5 at the corner of the p-type layer 3, light emission can be extracted outside without being blocked by the ball 6.

In order to wire-bond the electrode 5 formed on the p-type layer 3, another corner of the p-type layer 3 (for example, FIG.
(Points a and b shown in FIG. 1), but as shown in FIG. 1, they are at diagonal ends, that is, the electrode 4 of the n-type layer.
It is particularly preferable that the position where the wire bonding is performed and the position where the electrode 5 of the p-type layer is wire-bonded are at diagonal ends when viewed from the same surface side. This is because by setting the wire bonding positions at diagonally opposite ends, current flows uniformly from the electrode 5 to the electrode 4, and uniform surface light emission can be obtained. This is because the gallium nitride-based compound semiconductor light-emitting device is laminated on an insulating substrate called sapphire, so that no electrode can be taken from the substrate side. Therefore, when taking out both the positive and negative electrodes from the same gallium nitride-based compound semiconductor layer side, by setting the wire bonding position farthest from the electrode 4, it is possible to allow a current to flow uniformly in the p-type layer 3. This is because uniform surface light emission can be obtained. This is an effect peculiar to the gallium nitride-based compound semiconductor light emitting device.

FIG. 3 is a plan view of a light emitting device according to another embodiment of the present invention as viewed from the gallium nitride based compound semiconductor layer side as in FIG. 1, and FIG. 4 is a dashed line in FIG. It is an outline sectional view at the time of cutting at the position shown. Although the basic structure is the same as in FIGS. 1 and 2, this light emitting element uses the electrode 5 of the p-type layer 3 as a translucent electrode made of metal. The reason why the electrode 5 is made of metal is to obtain ohmic contact with the p-type layer 3. Further, the electrode 5 can be made translucent by, for example, depositing or sputtering a very thin metal such as Au, Ni, or Pt so as to be translucent. Further, it can be realized by vapor-depositing and sputtering a metal, annealing the metal, and diffusing the metal into the gallium nitride-based compound semiconductor, and scattering the metal to the outside to adjust the film thickness to a light-transmitting property. The thickness of the electrode 5 that becomes translucent varies depending on the type of metal, but the preferred thickness is in the range of 0.001 μm to 0.1 μm.

Further, when the electrode 5 is made translucent, FIG.
The electrode 5 can be formed on almost the entire surface of the p-type layer 3 as shown in FIG. By forming the electrode 5 over the entire surface as shown in FIG. 3, the current spreads over the entire surface of the p-type layer 3 as compared with the linear electrode of FIG. .

Further, when the electrode 5 is made translucent,
When wire bonding is directly performed on the light-transmitting electrode, the ball tends to be less likely to stick to the electrode 5 without being alloyed with the electrode 5 because the thickness of the electrode 5 is thin. It is preferable to form a pedestal electrode 8 for bonding. The pedestal electrode 8 can use a normal electrode material such as Au, Pt, or Al, and can be formed with a thickness of several μm. Further, the linear electrode 5 shown in FIG. 1 may be made translucent, and when the linear electrode 5 is made translucent, the pedestal electrode 8 may be provided at a corner of the electrode 5. Needless to say.

In the present invention, the corners of the n-type layer for wire-bonding the electrodes of the n-type layer refer to FIGS.
As shown in FIG. 1, the electrode formed at the corner of the n-type layer on the same plane is referred to as the corner of the p-type layer for wire bonding the electrode of the p-type layer. As shown, it indicates a corner of an electrode of a p-type layer formed on the same plane.

[0015]

In the light emitting device of the present invention, the electrode of the n-type layer is wire-bonded at the corner of the n-type layer.
Since the electrode of the mold layer is wire-bonded at the corner of the p-type layer, light emission can be efficiently taken out without being blocked by the electrode. In addition, since one chip can be mounted on one lead frame by wire bonding from the upper part, the chip size can be reduced and productivity can be improved. Furthermore, by arranging the electrodes of the n-type layer and the electrodes of the p-type layer on a diagonal line, that is, at the farthest position, the current can be uniformly spread and the luminous efficiency is further improved. Further, by forming the electrode of the p-type layer to be light-transmitting and forming it on almost the entire surface of the p-type layer, the current can be reduced to p-type.
The light uniformly flows over the entire surface of the mold layer, and light emission can be observed from the electrode side through the translucent electrode.

[0016]

EXAMPLE A wafer is prepared by sequentially stacking an n-type GaN layer and a p-type GaN layer on a substrate. Next, the p-type GaN
After forming a mask of a predetermined shape on the layer, p-type GaN
The layer is partially etched to expose the n-type GaN layer. However, the etching shape is as shown in FIG. 1, and the area of the exposed n-type layer is a minimum area where an electrode is formed thereon and wire bonding can be performed on the electrode.

Next, a mask for forming an electrode is formed on the p-type GaN layer, and N vapor is deposited on almost the entire surface of the p-type GaN layer by an evaporation apparatus.
Deposit i / Au to a thickness of approximately 300 Å. It is noted that Al is also 1 μm on the exposed n-type GaN layer.
The thickness is deposited. In this state, an electrode pattern in which the electrodes of the n-type layer and the electrodes of the p-type layer are located diagonally is completed.

After the deposition, the electrodes on the p-type layer are made transparent by annealing the wafer with an annealing apparatus. Further, a mask is formed again, and a pedestal electrode made of Al for bonding is placed at a predetermined position of the translucent electrode.
It is formed with a thickness of μm. In this state, a pattern in which the wire bonding position of the electrode of the n-type layer and the wire bonding position of the electrode of the p-type layer are on a diagonal line is completed.

Next, the wafer is cut into a square so that the previously formed pattern is located at the corner of the light emitting element, thereby forming a light emitting chip. After that, the light emitting chip was placed on one lead frame with the GaN layer side as the light emission observing surface, and gold wires were wire-bonded to the respective electrodes. Finally, the whole was molded with epoxy resin. The light-emitting diode of the present invention. FIG. 5 shows a schematic sectional view of this light emitting diode. In this figure, 10 is a lead frame, and 11 is an epoxy resin. When the light-emitting diode was made to emit light, the light-emitting diode was 1.5 times brighter than that of the same element which was wire-bonded to the center of the electrode of the p-type layer.

[0020]

As described above, since the bonding position of the light emitting device of the present invention is at the corner of the light emitting device,
Light emission is less blocked by an electrode, a bonding electrode, a ball, and the like, so that the light emitting efficiency of the light emitting element can be improved. Further, since both electrodes can be taken out from the gallium nitride-based compound semiconductor layer side and wire-bonded, the chip size can be reduced and the productivity is improved. More preferably, by arranging both electrodes on a diagonal line between the corners, the current of the p-type layer can be uniformly spread and uniform light emission can be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a light emitting device according to one embodiment of the present invention as viewed from a gallium nitride based compound semiconductor layer side.

FIG. 2 is a schematic cross-sectional view of the light emitting device of FIG.

FIG. 3 is a plan view of a light emitting device according to another embodiment of the present invention as viewed from a gallium nitride-based compound semiconductor layer side.

FIG. 4 is a schematic cross-sectional view of the light emitting device of FIG.

FIG. 5 is a schematic sectional view of a light emitting device according to one embodiment of the present invention.

[Explanation of symbols]

 1 ... substrate 2 ... n-type layer 3 ... p-type layer 4 ... electrode of n-type layer 5 ... electrode of p-type layer 6 ... ball 7 ... Gold wire 8 ... Pedal electrode

Continuation of the front page (56) References JP-A-3-218625 (JP, A) JP-A-62-28765 (JP, A) JP-A-62-2675 (JP, A) JP-A-5-129658 (JP, A) JP-A-2-101089 (JP, A) JP-A-63-311777 (JP, A) JP-A-59-28384 (JP, A)

Claims (3)

(57) [Claims] An n-type gallium nitride-based compound semiconductor layer and a p-type gallium nitride-based compound semiconductor layer are provided on a substrate.
A p-electrode is formed on the surface of the p-type gallium nitride-based compound semiconductor layer, and an n-electrode is formed on the surface of the n-type gallium nitride-based compound semiconductor layer exposed by removing a part of the p-type gallium nitride-based compound semiconductor layer; In the method of manufacturing a gallium nitride-based compound semiconductor light emitting device in which light emission is observed from the electrode side by energizing the p electrode and the n electrode on the same surface side, the step of forming the p electrode includes the steps of: Forming an ohmic light-transmitting electrode made of a metal thin film on the surface of the p-type gallium nitride-based compound semiconductor layer, and forming a diagonal with the n-electrode on a part of the surface of the light-transmitting electrode. Forming a pedestal electrode for wire bonding at a position; and forming the n-electrode, wherein the p-type gallium nitride-based compound semiconductor layer is positioned diagonally to the pedestal electrode. Forming a p-electrode by exposing a part of the n-type gallium nitride-based compound semiconductor layer underneath to expose the surface of the underlying n-type gallium nitride-based compound semiconductor layer, and then forming an electrode for wire bonding on the exposed portion. In the above, the light-transmitting electrode is formed on substantially the entire surface of the p-type gallium nitride-based compound semiconductor layer between the n-electrode and the pedestal electrode arranged diagonally and serving as an emission observation surface, and the n-electrode and the pedestal are formed. When energizing with the electrode, the current is uniformly spread on the p-type gallium nitride-based compound semiconductor layer below the translucent electrode so that substantially uniform light emission is observed from the translucent electrode. Of manufacturing a gallium nitride-based compound semiconductor light emitting device. 2. The method for manufacturing a gallium nitride-based compound semiconductor light emitting device according to claim 1, further comprising, after forming the translucent electrode, annealing the wafer on which the electrode is formed. 3. An n-type gallium nitride-based compound semiconductor layer and a p-type gallium nitride-based compound semiconductor layer on a substrate,
A p-electrode is formed on the surface of the p-type gallium nitride-based compound semiconductor layer, and a part of the substantially rectangular p-type gallium nitride-based compound semiconductor layer is removed and exposed on the surface of the n-type gallium nitride-based compound semiconductor layer. In a gallium nitride-based compound semiconductor light emitting device in which an electrode is formed and a p-electrode and an n-electrode are formed on the same surface side, the p-electrode is formed at one corner of the p-type gallium nitride-based compound semiconductor layer. A pedestal electrode for wire bonding formed in the portion, and a metal thin film for current diffusion and ohmic having a larger area than the pedestal electrode formed below and in contact with the p-type gallium nitride-based compound semiconductor The n-electrode is formed in a substantially rectangular n-type gallium nitride-based compound semiconductor layer at a position diagonal to the pedestal electrode, An electrode for wire bonding formed on the surface of the n-type gallium nitride-based compound semiconductor layer from which the aluminum-based compound semiconductor layer has been etched away, wherein the light-transmitting electrode is a pedestal electrode and an n-electrode at diagonal positions. And the p-type gallium nitride-based compound semiconductor layer, which is almost the entire surface of the p-type gallium nitride-based compound semiconductor layer serving as a light emission observation surface, and is electrically connected to the pedestal electrode and the n-electrode, and is located under the translucent electrode. A gallium nitride-based compound semiconductor light-emitting device having a light-emitting surface on which a current is uniformly spread in a semiconductor layer and substantially uniform light emission is observed.