JP2001217501A - Semiconductor light emitting element and method of forming electrode thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an electrode forming process of a semiconductor light emitting element by reducing a treating process. SOLUTION: When an electrode layer is formed on a semiconductor laminate composed of compound semiconductor by sputtering, heat treatment is performed while electrode material is sputtered by increasing high frequency power. As a result, an ohmic contact is formed simultaneously with the formation of the electrode layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming an electrode of a semiconductor light emitting device and a semiconductor light emitting device using the same to form an ohmic contact between a semiconductor layer and an electrode.

[0002]

2. Description of the Related Art Conventionally, as an electrode of a semiconductor light emitting device, an ohmic metal layer made of a material capable of forming an ohmic contact with a compound semiconductor, a barrier metal layer, and a material capable of wire bonding are used. A bonding pad layer is known.

This electrode is generally formed according to a manufacturing flow as shown in FIG.

First, an ohmic metal layer is formed on an arbitrary wafer by vapor deposition or sputtering.
An ohmic contact is formed by performing a heat treatment at a temperature of about 500C to about 500C. Thereafter, a barrier metal layer and a bonding pad layer are formed by sputtering, and processed into an arbitrary electrode shape.

[0005]

However, in the above-described conventional electrode forming method, after forming an ohmic metal layer by sputtering or vapor deposition, heat treatment is performed to form an ohmic contact, and then sputtering is performed again to form a barrier metal. And a bonding pad layer. This increases the number of processing steps,
And it becomes complicated. As the number of processing steps increases,
It takes time to form electrodes, and as a result,
There is a problem that the processing ability is reduced and a loss occurs in the manufacturing process of the semiconductor light emitting device.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and a method of forming an electrode of a semiconductor light emitting device which can reduce the number of processing steps and shorten the manufacturing time of the semiconductor light emitting device. It is an object of the present invention to provide a semiconductor light emitting device having an electrode formed using the same.

[0007]

According to the method of forming an electrode of a semiconductor light emitting device of the present invention, when forming an electrode layer on a semiconductor laminated structure made of a compound semiconductor by sputtering, the electrode material is sputtered by increasing the high frequency power. The heat treatment is performed while performing the heat treatment, thereby achieving the above object.

According to a method of forming an electrode of a semiconductor light emitting device of the present invention, an electrode comprising an ohmic metal layer, a barrier metal layer and a bonding pad layer is formed on a semiconductor laminated structure comprising a compound semiconductor. Forming the ohmic metal layer on the ohmic metal layer by evaporation or sputtering, forming the barrier metal layer on the ohmic metal layer by sputtering with increased high-frequency power, and heat-treating the ohmic metal layer,
Further, the bonding pad layer is formed on the barrier metal layer by vapor deposition or sputtering, thereby achieving the above object.

The method of forming an electrode of a semiconductor light emitting device according to the present invention is a method of forming an electrode comprising an ohmic metal layer, a barrier metal layer and a bonding pad layer on a semiconductor laminated structure comprising a compound semiconductor. The ohmic metal layer is formed on the ohmic metal layer by vapor deposition or sputtering, the barrier metal layer is formed on the ohmic metal layer by vapor deposition or sputtering, and the bonding pad is formed on the barrier metal layer by sputtering with increased high frequency power. The layer is formed and the ohmic metal layer is heat treated, thereby achieving the above objective.

It is preferable to heat-treat the electrode material by performing sputtering with the high frequency power of 3.0 kW or more.

When performing sputtering by increasing the high frequency power, it is preferable to use a sputtering apparatus in which a stage on which a wafer is set and a target which is an electrode material have substantially the same size.

When the high-frequency power is increased and sputtering is performed, it is preferable to control the plasma for controlling the magnetic field with an electromagnetic coil in order to make the temperature on the stage on which the wafer is set uniform.

AuBe is used as the ohmic metal layer.
AuZn or AuSi can be used, and Ti, TiN or Mo can be used as the barrier metal layer.

In the semiconductor light emitting device of the present invention, the electrodes are formed by using the method for forming electrodes of the semiconductor light emitting device of the present invention, thereby achieving the above object.

The operation of the present invention will be described below.

In the present invention, when forming an electrode layer on a semiconductor laminated structure made of a compound semiconductor by sputtering, heat treatment can be performed while sputtering the electrode material by increasing the high frequency power. Therefore, the heat treatment step performed after the formation of the electrode layer for forming the ohmic contact in the related art can be omitted.

For example, in an electrode structure composed of an ohmic metal layer, a barrier metal layer, and a bonding pad layer, after forming an ohmic metal layer on a semiconductor multilayer structure by vapor deposition or sputtering, a high frequency power is increased on the ohmic metal layer. By forming the barrier metal layer by the above, it is possible to simultaneously perform the heat treatment of the ohmic metal layer at the time of forming the barrier metal layer. Alternatively, the heat treatment of the ohmic metal layer can also be performed by forming the bonding pad layer by sputtering with increased high-frequency power.

High frequency power (RF
When the power is set to 3.0 kW or more, it is possible to raise the temperature in the plasma generation region to 300 ° C. to 500 ° C. by utilizing the heat of the plasma generated during sputtering. To form an ohmic contact.

During sputtering, since the temperature outside the plasma generation region is low, all wafers for which ohmic contacts need to be formed are exposed to the plasma atmosphere. Therefore, when performing sputtering by increasing the high-frequency power, a stage on which the wafer is set,
It is preferable to use a sputtering apparatus in which a target which is an electrode material has substantially the same size.

Further, when a temperature difference occurs on the stage on which the wafer is set, a portion where an ohmic contact is formed by heat treatment and a portion where an ohmic contact is not formed are formed. Therefore, when performing sputtering by increasing the high-frequency power, it is preferable to control the magnetic field with an electromagnetic coil in order to make the temperature on the stage uniform. This makes it possible to arbitrarily adjust the plasma generation region and strength during sputtering.

The barrier metal layer is made of AuBe, AuZ
It is provided to prevent impurities from diffusing from the ohmic contact layer made of n or AuSi or the like to the bonding pad layer made of Al or Au or the like. As the barrier metal layer, for example, Ti, TiN, Mo, or the like can be used.

[0022]

Embodiments of the present invention will be described below.

Here, when the barrier metal layer and the bonding pad layer are formed by sputtering, the high-frequency power is increased during the sputtering, and the heat treatment of the ohmic metal layer is performed by utilizing the generated plasma heat. An example of forming an ohmic contact between a layer and an ohmic metal layer will be described.

The RF power applied at the time of sputtering the barrier metal layer and the bonding pad layer is 3.0
kW or more. The reason for this is that by generating plasma with RF power of 3.0 kW or more, the temperature in the region where plasma is generated can be raised to 300 ° C. to 500 ° C. Thus, the previously formed ohmic metal layer is heat-treated to form an ohmic contact. Note that, as the high-frequency power applied during sputtering is increased, the film formation rate is increased, so that the sputtering time may be shortened and the film thickness control may be difficult. Therefore, it is not preferable that the high frequency power is too high.

In the present invention, since the heat treatment for forming the ohmic contact is performed simultaneously during the sputtering, it is preferable that the wafer on which the ohmic contact is formed is always exposed to the plasma atmosphere. The reason is that the temperature becomes low outside the plasma generation region.

In a sputtering apparatus, plasma is generated between a target, which is an electrode material, and a stage on which a wafer is set. Therefore, the plasma generation region is determined by the size of the target and the size of the stage. . In a general sputtering apparatus, the target is smaller than the stage, and the size of the target is usually at most about 20 cmφ.

In general, a sputtering apparatus used to form electrodes of a semiconductor light emitting element has a large vacuum chamber (chamber) of about 80 cm to 100 cm so as to process as many wafers as possible in one batch. belongs to. However, as described above, the plasma generation region (sputtering region) has a maximum of 20 c
Since the diameter is about mφ, it is impossible to form an electrode by sputtering an area of 80 cm to 100 cm at a time.

Therefore, by rotating the stage on which the wafers are set, the wafers are repeatedly passed through the plasma generation region (sputtering region) to process many wafers in one batch.

FIG. 1 shows a schematic configuration of this sputtering apparatus.
Shown in This sputtering apparatus has a chamber 20a
An exhaust port 8a connected to a cryopump (for main exhaust) 8 via a main valve 6 to connect the inside to a reduced pressure state, and an oil rotary pump (for auxiliary exhaust) 9 via a roughing valve 7 An exhaust port 9a and a gas introduction port 5 for introducing a gas for generating the plasma 10 are provided. In the chamber 20a, a target 4 smaller than the stage 21a on which the wafer 11 is set is arranged at a certain interval from the stage 21a. On the surface of the target 4 opposite to the stage 21a of the target 4, a cathode electrode 3 for generating a voltage is provided, and the stage 21a is grounded. Then, a cathode shield 2 is provided so as to cover the cathode electrode 2,
An insulator 1 is provided at a portion in contact with the chamber.

However, in the present invention, it is preferable that the wafer for forming the ohmic contact is always exposed to the plasma atmosphere, so that the sputtering apparatus shown in FIG. 1 is not suitable for the present invention.

Therefore, in the present invention, as shown in FIG. 2, for example, it is preferable to use a sputtering apparatus having a small chamber 20 in which the stage 21 has the same size as the target 4 (for example, about 20 cmφ). Thereby, during sputtering, all the wafers 11
It can be made to be exposed to zero atmosphere.

Further, when plasma is generated by a sputtering apparatus, generally, as shown in FIG. 3, a permanent magnet 12 is attached to the target side to generate a magnetic field, thereby making it easier to generate plasma. This is because applying a magnetic field generates plasma even when the high-frequency power is low. Here, the permanent magnet 12 is mounted inside the cathode electrode 3.

However, in this method, plasma is intensively generated in the portion where the magnet 12 is provided. The reason for this is that the magnetic field of the portion where the magnet is provided is stronger than that of the portion where the magnet 12 is not provided. Therefore, plasma is not uniformly generated between the target and the stage, and a temperature difference occurs in the stage surface. When such a temperature difference occurs, a portion where the ohmic contact is formed and a portion where the ohmic contact is not formed due to the heat treatment, and the ohmic contact becomes insufficient.

Therefore, in the present invention, it is preferable to uniformly generate plasma between the target and the stage to make the temperature distribution in the stage plane uniform. For this purpose, it is preferable to use a method in which a magnetic field is generated by an electromagnet, instead of a method in which a magnetic field is generated by a permanent magnet as in the related art.

For example, as shown in FIG. 4, several electromagnetic coils 13 and 14 are attached to the target side, and the amount of current flowing through the electromagnetic coils 13 and 14 is arbitrarily changed. This makes it possible to uniformly generate plasma between the target and the stage by arbitrarily changing the range and strength of the magnetic field.

An example in which the heat treatment of the ohmic metal layer is performed by utilizing the plasma heat generated during sputtering when forming the barrier metal layer by sputtering will be described below with reference to FIG.

First, as shown in FIG. 5A, a wafer 15 on which a semiconductor laminated structure made of a compound semiconductor has been epitaxially grown is etched with a sulfuric acid-based etchant, and then sufficiently washed with pure water and dried. . This is a pretreatment step for improving the adhesion between the wafer and the electrodes. Here, as the wafer 15, a GaAs layer and GaAl are formed on a GaAs substrate by epitaxial growth.
One obtained by laminating an As layer is exemplified.

Next, in order to obtain a good ohmic contact, AuBe, Au and Au as shown in FIG.
An ohmic metal layer 16 made of Zn, AuSi, or the like is formed by sputtering or vapor deposition.

Next, the wafer 15 and the ohmic metal layer 1
In order to prevent impurities such as Ga, Zn and Be from being diffused to the surface of the bonding pad layer, FIG.
As shown in (1), a barrier metal layer 17 of Ti, TiN, Mo or the like is formed under the following conditions. The RF power applied at the time of sputtering is 3.0 kW or more, and the sputtering time is 3 minutes or more. Further, for example, using a sputtering apparatus as shown in FIGS. 2 and 4, a wafer for forming an ohmic contact at the time of sputtering is always in the plasma generation region. At the same time as the barrier metal layer 17 is formed by such sputtering, the ohmic metal layer 16 is heat-treated to form an ohmic contact.

Next, as shown in FIG. 5D, an Al film or an Au film serving as the bonding pad layer 18 is formed by sputtering or vapor deposition.

As shown in FIG. 5E, a necessary electrode pattern (resist film) 19 is formed on the wafer on which the electrode layer is formed as shown in FIG.

Thereafter, as shown in FIG. 5F, the metal film (here, the bonding pad layer 18 and the barrier metal layer 17) is sequentially removed from the bonding pad layer 18 by wet etching to form an electrode pattern. Finally, the resist film 19 is removed with an organic resist stripper.

Thus, an ohmic contact between the compound semiconductor and the electrode can be formed by a simple process.

[0044]

As described in detail above, according to the present invention,
When forming an electrode layer on a semiconductor laminated structure made of a compound semiconductor by sputtering, the high-frequency power is increased and, for example, the wafer is exposed to a plasma atmosphere for 3 minutes or more with an RF power of 3.0 kW or more, thereby forming an electrode material. Can be heat-treated while sputtering. Since the ohmic contact can be formed simultaneously with the sputtering of the electrode layer, the heat treatment step conventionally performed after the formation of the electrode layer can be omitted. Therefore,
A semiconductor light emitting device can be manufactured at a low cost by shortening the manufacturing time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a general sputtering apparatus used for forming an electrode of a semiconductor light emitting device.

FIG. 2 is a cross-sectional view showing a configuration of a sputtering apparatus suitable for a method for forming an electrode of a semiconductor light emitting device of the present invention.

FIG. 3 is a view showing a permanent magnet provided on a target side in a general sputtering apparatus used for forming an electrode of a semiconductor light emitting element, (a) is a top view,
(B) is a side view.

FIG. 4 is a diagram showing an electromagnetic coil provided on a target side in a sputtering apparatus suitable for a method for forming an electrode of a semiconductor light emitting device of the present invention, wherein (a) is a top view,
(B) is a side view.

5A to 5F are cross-sectional views illustrating a method for forming an electrode of a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 6 is a flowchart for explaining an electrode forming process of a conventional semiconductor light emitting device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulator 2 Cathode shield 3 Cathode electrode 4 Target 5 Gas inlet 6 Main valve 7 Roughing valve 8 Cryopump (for main exhaust) 8a, 9a Exhaust port 9 Oil rotary pump (for auxiliary exhaust) 10 Plasma 11, 15 Wafer 12 permanent magnet 13, 14 electromagnetic coil 16 ohmic metal layer 17 barrier metal layer 18 bonding pad 19 resist 20, 20a chamber 21, 21a stage

Claims (8)

[Claims] 1. A method for forming an electrode of a semiconductor light emitting element, wherein a heat treatment is performed while increasing an RF power and sputtering an electrode material when forming an electrode layer on a semiconductor laminated structure made of a compound semiconductor by sputtering. 2. A method for forming an electrode comprising an ohmic metal layer, a barrier metal layer, and a bonding pad layer on a semiconductor laminated structure made of a compound semiconductor, wherein the ohmic metal layer is formed on the semiconductor laminated structure by vapor deposition or sputtering. Is formed on the ohmic metal layer, the barrier metal layer is formed by sputtering with increased high-frequency power, the heat treatment is performed on the ohmic metal layer, and the bonding pad layer is formed on the barrier metal layer by vapor deposition or sputtering. A method for forming an electrode of a semiconductor light emitting element to be formed. 3. A method for forming an electrode comprising an ohmic metal layer, a barrier metal layer, and a bonding pad layer on a semiconductor laminated structure made of a compound semiconductor, wherein the ohmic metal layer is formed on the semiconductor laminated structure by vapor deposition or sputtering. To form the barrier metal layer on the ohmic metal layer by vapor deposition or sputtering, and further form the bonding pad layer on the barrier metal layer by sputtering with increased high-frequency power and the ohmic metal layer. A method for forming an electrode of a semiconductor light emitting element to be heat-treated. 4. The method for forming an electrode of a semiconductor light emitting device according to claim 1, wherein the electrode material is heat-treated by performing sputtering with the high-frequency power being 3.0 kW or more. 5. A stage on which a wafer is set when performing sputtering by increasing the high-frequency power;
The method for forming an electrode of a semiconductor light emitting device according to any one of claims 1 to 4, wherein a sputtering apparatus having a target of an electrode material having substantially the same size is used. 6. A magnetic field is controlled by an electromagnetic coil in order to make the temperature on a stage on which a wafer is set uniform when performing sputtering by increasing the high-frequency power. 13. The method for forming an electrode of a semiconductor light emitting device according to 7. An AuB film as the ohmic metal layer.
7. The method for forming an electrode of a semiconductor light emitting device according to claim 2, wherein e, AuZn, or AuSi is used, and Ti, TiN, or Mo is used as the barrier metal layer. 8. A semiconductor light emitting device having an electrode formed by using the electrode forming method for a semiconductor light emitting device according to claim 1.