JPH10190055A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture at low price by simultaneously forming both electrodes by a method wherein an n side electrode and a p side electrode are formed of the same metal material. SOLUTION: Semiconductor layers 2 to 5 for forming a light emitting area on a surface of a substrate 1 are laminated to form a semiconductor lamination part, and a p side electrode 8 is formed on the surface via a diffusion metal layer 7. Further, an n side electrode 9 is formed in the n type layer in which a part of the laminated semiconductor layers 3 to 5 is removed. Therein, the p side electrode 8 and n side electrode 9 comprise a lamination structure of metal thin films 8a, 9a, Ti layers 8b, 9b, and Au layers 8c, 9c containing Ni or Zn each, and both the electrodes 8, 9 are formed with the same material and thickness. On the substrate 1, the low temperature buffer layer 2, the n type layer 3, for example, an active layer 4 composed of an InGaN system compound semiconductor, and the p type layer 5 composed of a p type AlGan system compound semiconductor layer 5a and a GaN layer 5b are sequentially laminated, respectively.

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 which emits blue (from ultraviolet to yellow) light in which a gallium nitride compound semiconductor is laminated on a substrate. More specifically, the present invention relates to a semiconductor light emitting device in which the materials provided in the n-type layer and the p-type layer are made common while improving the ohmic contact and the adhesive strength of the electrodes.

[0002]

2. Description of the Related Art Conventionally, a semiconductor light emitting device that emits blue light has a structure as shown in FIG. 3, for example. That is, a low-temperature buffer layer 22 made of, for example, n-type GaN and an n-type layer (cladding layer) 23 on which GaN is epitaxially grown at a high temperature are formed on a sapphire substrate 21.
And a material whose band gap energy is smaller than that of the cladding layer and determines the emission wavelength, for example, an InGaN-based material (meaning that the ratio of In to Ga can be variously changed.
Active layer (light emitting layer) 24 made of a compound semiconductor
And a p-type layer (cladding layer) 25 made of p-type GaN, a p-side (upper) electrode 28 is provided on the surface thereof, and an n-type layer in which a part of the stacked semiconductor layers is exposed by etching. It is formed by providing an n-side (lower) electrode 29 on the surface of the layer 23. The n-type layer 23 and the p-type layer 25 include an AlGaN-based (which means that the ratio of Al and Ga can be variously changed, hereinafter the same) compound semiconductor layer on the active layer 23 side in order to improve the effect of confining carriers. May be used.

In this structure, the p-side electrode 28 is made of Ti and A
The n-side electrode 29 is formed of a metal layer in which Ti and Al are laminated and alloyed. The p-side electrode 28 is often provided via a diffusion metal layer (not shown) made of an alloy of Ni and Au provided on the surface of the stacked semiconductor layers. Therefore, although the ohmic contact property between the p-type layer and the diffusion metal is not preferable in relation to the dopant of the p-type layer,
The contact and adhesion between the diffusion metal layer and the p-side electrode are performed well. On the other hand, although the n-side electrode 29 is provided directly on the surface of the n-type layer 23, it is considered that a sufficient ohmic contact can be obtained by an alloy of Ti and Al.

[0004]

As described above, in a conventional semiconductor light emitting device using a gallium nitride compound semiconductor, different materials are used for an n-side electrode and a p-side electrode in consideration of ohmic contact characteristics. It is used. In a semiconductor light emitting device using a gallium nitride-based compound semiconductor, as shown in FIG. 3 described above, a semiconductor layer is laminated on an insulating substrate made of sapphire or the like. Are often provided on the same surface side. However, since the materials of the n-side electrode and the p-side electrode are different, both electrodes are separately formed. Therefore, the man-hour for forming the electrode is doubled, which causes an increase in cost.

The n-side electrode is made of an alloy of Ti and Al from the viewpoint of improving the ohmic contact characteristics with the n-type layer. There is a problem that the bonding strength of bonding is weak.

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation. In a semiconductor light emitting device having a laminated body of a gallium nitride compound semiconductor, the n-side is improved while improving the ohmic contact characteristics and the bonding strength of wire bonding. An object of the present invention is to provide a semiconductor light emitting device that can be formed at a low cost by simultaneously forming both electrodes by using the same material for the electrode and the p-side electrode.

[0007]

According to the present invention, there is provided a semiconductor light emitting device comprising: a substrate; a semiconductor laminated portion including an n-type layer and a p-type layer made of a gallium nitride compound semiconductor provided on the substrate; An n-side electrode and a p-side electrode connected to the p-type layer and the p-type layer, respectively, wherein the n-side electrode and the p-side electrode are formed of the same metal material.

Here, the gallium nitride compound semiconductor is a compound of a group III element Ga and a group V element N or
Compounds in which part of the group III element Ga is replaced by another group III element such as Al or In and / or compound in which part of the group V element N is replaced by another group V element such as P or As. Semiconductor.

The n-side electrode and the p-side electrode may each be composed of a thin film layer containing Ni or Zn and an Au layer provided on the thin film layer, or a laminate of a Ti layer and an Au layer. . The presence of the thin film layer or the Ti layer on the surface in contact with the semiconductor layer provides good ohmic contact, and the presence of the Au layer on the surface provides good wire bonding strength. When the thin film layer includes the thin film layer containing Ni or Zn and the Au layer, the Ti layer is provided between the thin film layer and the surface of the Au layer.

[0010]

Next, a semiconductor light emitting device of the present invention will be described with reference to the drawings. FIG. 1 is a sectional explanatory view of one embodiment of the semiconductor light emitting device of the present invention in which a gallium nitride-based compound semiconductor layer is laminated on a sapphire substrate.

As shown in FIG. 1, the semiconductor light emitting device of the present invention comprises semiconductor layers 2 to 5 for forming light emitting regions on the surface of a substrate 1 made of, for example, sapphire (Al ₂ O ₃ single crystal). The semiconductor device is laminated to form a semiconductor laminated portion, and a p-side electrode (upper electrode) 8 is formed on the surface thereof via a diffusion metal layer 7.
Are formed. Further, an n-side electrode (lower electrode) 9 is formed on the n-type layer 3 exposed by removing a part of the stacked semiconductor layers 3 to 5. In this example, the p-side electrode 8 and the n-side electrode 9 both have a laminated structure of metal thin films 8a, 9a containing Ni or Zn, Ti layers 8b, 9b and Au layers 8c, 9c. The present invention is characterized in that both electrodes 8 and 9 are formed of the same material and have the same thickness. Diffusion metal layer 7 is made of, for example, an alloy of Ni and Au.

The semiconductor layer laminated on the substrate 1 has a low-temperature buffer layer 2 made of, for example, GaN of 0.01 to 0.2 μm.
m and then an n-type layer 3 serving as a cladding layer is 1
The active layer 4 made of a material having a band gap energy smaller than that of the clad layer, for example, an InGaN-based compound semiconductor, is deposited to a thickness of about 5 μm.
A p-type layer (cladding layer) 5 composed of a p-type AlGaN-based compound semiconductor layer 5a and a GaN layer 5b of about 0.5 to 0.3 μm is sequentially laminated to about 0.2 to 1 μm.

Although the p-type layer 5 is a multilayer of the AlGaN-based compound semiconductor layer 5a and the GaN layer 5b, it is preferable to provide a layer containing Al from the viewpoint of carrier confinement effect. The GaN layer alone may be used. Also,
The n-type layer 3 may also be provided with an AlGaN-based compound semiconductor layer to form a multi-layer, or they may be formed of another gallium nitride-based compound semiconductor layer. Furthermore, in this example, the active layer 4 is sandwiched between the n-type layer 3 and the p-type layer 5, but the double hetero-junction structure is used. Good.

In the semiconductor light emitting device of the present invention, as described above, the p-side electrode 8 and the n-side electrode 9 are made of the same material having the same thickness. That is, both electrodes 8 and 9 are shown in FIG.
As shown in FIG. 5, metal thin films 8a and 9a (simply indicated by a in the figure) made of an alloy layer of Ni and Au are formed on the semiconductor layer by, for example, forming Ni and Au in a thickness of 5 nm each and sintering them. Partly penetrated, 2 in total
It is formed to a thickness of about 7 nm. On top of this, Ti layers 8b and 9b (simply indicated by b in the figure) are about 0.1 μm,
And the Au layers 8c and 9c (simply indicated by c in the figure) have a thickness of 0.2.
They are formed by being laminated about 3 μm each and patterned into an electrode shape.

Next, even if the p-side electrode 8 and the n-side electrode 9 of the semiconductor light emitting device of the present invention are formed of the same material,
The reason why the ohmic contact characteristics are good and the adhesive strength of wire bonding becomes sufficient will be described.

Since the p-side electrode 8 is provided on the diffusion metal layer 7, the ohmic contact between the p-type layer 5 and the diffusion metal layer 7 is aside, and the space between the p-side electrode 8 and the diffusion metal layer 7 is relatively good. Connection is obtained. On the other hand, the n-side electrode 9
It has been considered that a laminated film of Ti and Al is optimal for the ohmic contact with the n-type layer 3 which is provided directly on the n-type layer 3 and is made of a Si-doped gallium nitride compound semiconductor.
However, when a gold wire or the like is wire-bonded to the outermost layer of the electrode and an Al oxide film is formed, the bonding strength of the wire bonding decreases. Furthermore, even if the p-side electrode 8 and the n-side electrode 9 are provided in the same direction, the electrodes must be formed separately because of the different materials.

The inventors of the present invention have conducted intensive studies to improve the ohmic contact characteristics and the bonding force of wire bonding. As a result, a chip containing Ni or Zn such as an Au / Ni alloy and doped with Si has been developed. A thin film alloyed with a gallium arsenide compound semiconductor, 2-7
It has been found that a relatively good ohmic contact characteristic can be obtained irrespective of the metal material provided on the surface by being formed as thin as about nm. That is, the conventional n-type layer 3 is provided directly with the above-described alloy layer of Ti and Al, and as in the present invention, provided with the above-described laminated structure of the Ti layer 9b and the Au layer 9c via the metal thin film 9a. As a result of comparing the series resistance with the case, it was found that there was almost no difference between the two, and rather the series resistance was smaller when the metal thin film 9a was interposed. This is considered to be because the metal thin film plays the role of an ohmic contact metal and improves electrical conduction.

As a result, the p-side electrode and the n-side electrode can be formed simultaneously under the same conditions, and
It can be a u layer, and the adhesive force of wire bonding can be sufficiently increased. That is, a gold wire was used as the wire for wire bonding, and the bonding between Au was performed securely, so that the bonding was reliably performed, and the defect rate due to the conventional bonding peeling was about 20%, but it became 0%.

As described above, since the metal thin films 8a and 9a achieve ohmic contact, a thin metal thin film alloyed with a gallium nitride compound semiconductor may be interposed. Therefore, even if it is not provided so as to swell on the surface of the semiconductor layer, a portion protruding from the surface may be removed by aqua regia just by being alloyed in the semiconductor layer. From this viewpoint, even if it is not the alloy of Ni and Au described above, as shown in FIGS. 2B to 2G, Ni, Au-Ge-Ni, Zn-Ni, In-N
A thin film of another metal or alloy which is easily alloyed with a gallium nitride-based compound semiconductor such as i, In-Zn, In-Zn-Ni may be used.

Further, as described above, the metal thin films 8a, 9
If a is composed of an alloy thin film, further alloying is unlikely to proceed even if the surface is not provided with a Ti layer. Therefore, even if the Au layer is provided directly without the Ti layer, the Au layer remains on the surface, and an electrode having good ohmic contact characteristics and good adhesive strength for wire bonding can be obtained. In this case, since the Au layer is somewhat alloyed with the metal of the metal thin film during the heat treatment, it is preferably provided with a thickness of about 1 μm or more.

In each of the above examples, an ohmic contact is obtained mainly by interposing a metal thin film to be alloyed, alloying with an Au layer provided on the surface is prevented, and an Au layer is formed on the outermost surface. Was formed, but by providing Ti instead of a metal thin film and alloying it with the semiconductor layer, it was found that a sufficient ohmic contact could be obtained even without Al. as a result,
Even if an Au layer was directly provided on the surface, similarly good ohmic contact characteristics and adhesive strength of wire bonding were obtained.

Next, a method of manufacturing the semiconductor light emitting device shown in FIG. 1 will be described.

Metalorganic chemical vapor deposition (MOCVD)
Thus, a reactive gas such as trimethyl gallium (TMG) and ammonia (NH ₃ ) and SiH ₄ as an n-type dopant gas are supplied together with H ₂ of a carrier gas, and first, for example, insulation made of sapphire On the substrate 1, for example, at a low temperature of about 400 to 600 ° C.
The low-temperature buffer layer 2 made of GaN has a thickness of 0.01 to 0.2 μm.
The temperature is raised to about 600 to 1200 ° C., and an n-type n-type layer (cladding layer) 3 having the same composition is formed to a thickness of about 1 to 5 μm. Further, the dopant gas is stopped, and trimethylindium (hereinafter, referred to as TMIn) is added as a reaction gas, so that the active layer 4 made of an InGaN-based compound semiconductor has a thickness of 0.1%.
A film having a thickness of about 005 to 0.3 μm is formed.

Next, TMIn of the reaction gas was changed to trimethylaluminum (hereinafter referred to as TMA), and cyclopentadienyl magnesium (C
p ₂ Mg) or dimethylzinc (DMZn) to introduce a p-type AlGaN-based compound semiconductor layer 5a of 0.1 to 0.1 μm.
The p-type layer 5 is formed by laminating the p-type GaN layer 5b to a thickness of about 0.1 to 0.5 μm while stopping the TMA of the reaction gas again about 0.5 μm.

Thereafter, a protective film such as SiN is provided on the surface, and annealing is performed at about 400 to 800 ° C. for about 10 to 60 minutes to activate the p-type dopant.
And Au are deposited and sintered to form a diffusion metal layer 7 of about 2 to 100 nm. Next, a part of the laminated semiconductor layer is etched by reactive ion etching using a chlorine gas or the like so that the n-type layer 3 is exposed to form a lower electrode.

Next, for example, a resist is applied and patterned so as to expose only the formation site of the p-side electrode and the n-side electrode, and Ni and Au are deposited by vacuum evaporation in a thickness of about 5 nm each, and 300 to 500 A heat treatment is performed at about 5 ° C. for about 5 to 15 minutes to perform sintering. As a result, Ni and Au are alloyed, part of which penetrates into the semiconductor layer and has a thickness of about 2 to 7 nm on its surface, and metal thin films 8a and 9a are formed only in the portions where both electrodes are formed. Thereafter, a resist film is further provided in the same manner, and patterning is performed so that only the electrode forming portion is exposed, and the Ti layers 8b and 9b are patterned.
And Au layers 8c and 9c are about 0.1 μm and 0.1 μm, respectively.
Films are formed by vacuum evaporation or the like by about 3 μm (lift-off method). Then, the upper electrode 8 and the lower electrode 9 are formed by sintering at about 300 to 500 ° C. for about 5 to 15 minutes. As a result, the semiconductor light emitting device shown in FIG. 1 is obtained.

In the case of forming an alloy thin film other than the Au—Ni alloy, thin films of the respective metals are similarly laminated and sintered to form an alloy thin film of those metals. For example, when forming an Au—Ge—Ni thin film, the Ni layer should be 5
It is formed by laminating about 5 nm of a Ge layer, about 5 nm of a Ge layer, and about 5 nm of an Au layer by vacuum evaporation, and performing heat treatment at about 200 to 500 ° C. for about 5 to 40 minutes.
Other Zn-Ni, In-Ni, In-Zn, In-Zn-N
The same applies to i.

As described above, according to the present invention, since the p-side electrode and the n-side electrode are formed of the same material and of the same thickness, they are formed simultaneously in the same step. Therefore, the number of steps is reduced, and the number of steps is also reduced, which greatly contributes to cost reduction.

[0029]

According to the present invention, the adhesive force of wire bonding is improved while maintaining the ohmic contact characteristics, and the reliability is greatly improved. Moreover, since the p-side electrode and the n-side electrode are made of the same material, both electrodes can be formed simultaneously, and the number of steps can be reduced. as a result,
A highly reliable and inexpensive semiconductor light emitting device can be obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view of one embodiment of a semiconductor light emitting device of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a p-side electrode and an n-side electrode of FIG. 1;

FIG. 3 is a perspective view illustrating an example of a conventional semiconductor light emitting device.

[Explanation of symbols]

 Reference Signs List 1 substrate 3 n-type layer 4 active layer 5 p-type layer 8 p-side electrode 8a metal thin film 8b Ti layer 8c Au layer 9 n-side electrode 9a metal thin film 9b Ti layer 9c Au layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Sonobe 21st Ryoin Mizozakicho, Ukyo-ku, Kyoto City (72) Inventor Noriwa Ito 21st Rohm Co., Ltd., Saiin-Mizozakicho, Ukyo-ku, Kyoto

Claims (4)

[Claims] 1. A substrate, a semiconductor laminated portion including an n-type layer and a p-type layer made of a gallium nitride-based compound semiconductor provided on the substrate, and connected to the n-type layer and the p-type layer, respectively. A semiconductor light-emitting device comprising an n-side electrode and a p-side electrode, wherein the n-side electrode and the p-side electrode are formed of the same metal material. 2. The semiconductor light emitting device according to claim 1, wherein the n-side electrode and the p-side electrode each include a thin film layer containing Ni or Zn, and an Au layer provided on the thin film layer. 3. The semiconductor light emitting device according to claim 2, wherein a Ti layer is provided between said thin film layer and said Au layer. 4. The semiconductor light emitting device according to claim 1, wherein the metal layers of the n-side electrode and the p-side electrode are each made of Ti and Au layers.