JPH10308359A - Semiconductor device and method of forming its electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device having an electrode capable of having a good ohmic contact and being brazed and a method of forming such an electrode. SOLUTION: An electrode 4 having an ohmic contact with a GaAs(gallium arsenide) semiconductor region 1a comprises a multilayer body including a first layer 5 made of AuGeNi (gold, germanium, nickel), a second layer 6 made of AuNi, a third layer 7 made of Ni, and a fourth layer 8 made of Au. The second layer 6 prevents deposition of Ge on the surface of the electrode 4. The third layer 7 improves soldering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device such as a Schottky barrier diode containing GaAs or a semiconductor containing the same as a main component, and a method for forming the electrode.

[0002]

2. Description of the Related Art An AuGeNi layer or AuSi is used as an ohmic contact electrode of a GaAs (gallium arsenide) semiconductor device.
An electrode having a two-layer structure in which a layer and an Au layer are sequentially stacked is known. By providing an AuGeNi layer or an AuSi layer, an electrode that is in good ohmic contact with a GaAs semiconductor can be obtained.

[0003]

However, it has been difficult to satisfactorily fix the above electrodes on a metal support by soldering. This is considered to be due to the fact that Ge of the AuGeNi layer or Si of the AuSi layer precipitates on the surface of the Au layer to form an oxide film. Since Ge and Si have a remarkably poor affinity with solder, if Ge or Si precipitates on the surface of the Au layer, the solder adhesion of the Au layer is reduced. Also,
Since the conventional electrode structure has a two-layer structure of an AuGeNi layer and an Au layer, the Au layer is taken into the solder at the time of soldering, and when the Au layer disappears, the AuGeNi layer comes into contact with the solder. Since the AuGeNi layer is not well adapted to the solder, peeling may occur at the interface between the solder layer and the electrode.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor device having an electrode capable of obtaining good ohmic contact and achieving good brazing, and a method of forming the electrode.

[0005]

Means for Solving the Problems To solve the above problems and achieve the above object, an invention of the present invention is to provide a semiconductor region made of GaAs (gallium arsenide) or a compound semiconductor containing Ga and As as main components. A semiconductor element comprising: a semiconductor substrate having: a first layer containing AuGeNi (gold / germanium / nickel) disposed adjacent to the semiconductor region; AuNi disposed adjacent to the first layer.
A second layer containing (gold / nickel), a third layer made of Ni (nickel) disposed adjacent to the second layer, and Au (gold) disposed adjacent to the third layer. And the fourth, fourth, and fourth layers, wherein the first, second, third, and fourth layers relate to semiconductor elements that are sequentially stacked. It should be noted that the semiconductor material and the AuGeNi
It is desirable to provide the first layer so as to include at least a part of the alloying layer with the above. Further, an Au layer can be interposed between the first layer and the second layer. Further, an AuNi layer can be interposed between the third layer and the fourth layer. The invention of the method of the present application uses GaAs (gallium arsenide) or Ga and A
a semiconductor substrate having a semiconductor region made of a compound semiconductor containing s as a main component, and a method for forming the electrode in a semiconductor element having an electrode in contact with the semiconductor region, wherein the main surface of the semiconductor region is Forming an AuGeNi layer by depositing AuGeNi on the substrate;
depositing Au on the surface of the eNi layer to form a first Au layer; performing a heat treatment on a semiconductor substrate including the AuGeNi layer and the first Au layer; Depositing Ni on the surface of the layer to form a Ni layer; depositing Au on the surface of the Ni layer to form a second Au layer; the AuGeNi layer and the first A
heat treatment is performed on the semiconductor substrate including the u layer, the Ni layer, and the second Au layer to alloy a part of the Ni layer with at least a part of the first Au layer to form an AuNi layer. And a method for forming an electrode. In addition, AuGeNi and Au
Is desirably continuously deposited, and Ni and Au are continuously deposited.

[0006]

According to the first to fourth aspects of the present invention,
Since the AuGeNi layer or the first layer containing AuGeNi is arranged adjacent to the semiconductor region, good ohmic contact can be obtained as in the related art. AuNi is provided between the first layer containing AuGeNi and the fourth layer made of Au.
Since the second layer made of Ni and the third layer made of Ni are interposed, Au of the fourth layer or A of the fourth layer is used during brazing.
Even if u and Ni of the third layer are absorbed by the brazing material, the brazing material comes into contact with the Ni of the third layer which is familiar or the AuNi layer between the third and fourth layers, Electrode brazing can be successfully achieved. In addition, when Ni diffuses into the semiconductor region, a problem such as reduction in ohmic contact is caused. However, since the second layer containing AuNi is provided, it is necessary to suppress the diffusion of Ni in the second layer. Can be. In addition, the second and third layers prevent Ge of the first layer from depositing on the surface of the fourth layer, and contribute to maintaining good wettability of the brazing material of the fourth layer. Further, since the second layer is not an Au layer which is easily eroded by solder but an AuNi layer which is hardly eroded by solder, it is necessary to prevent erosion by solder from the side of the second layer which occurs when soldering an electrode. And peeling of the third layer can be prevented. In addition, a semiconductor material containing GaAs and AuGe
By providing an alloyed layer with Ni, better ohmic contact can be obtained. In addition, as shown in claim 3, the first and second
If an Au layer is interposed between the layers, the diffusion of Ni into the semiconductor region can be more effectively prevented. Further, AuNi is provided between the third layer and the fourth layer.
Even if a layer is interposed, the solderability is not reduced. According to the method of forming an electrode of the fifth aspect, AuGeNi
The first heat treatment is performed at the stage when the layer and the first Au layer are formed, and the second heat treatment is performed after the second Au layer is formed. Therefore, the first heat treatment is performed for ohmic contact. It is possible to perform the second heat treatment for the purpose of forming the AuNi layer, thereby preventing unnecessary diffusion of Ni and maintaining good ohmic properties. According to the invention of claim 6, each layer can be efficiently formed by continuous vapor deposition.

[0007]

Next, a Schottky barrier diode as a semiconductor device according to an embodiment of the present invention and a method of manufacturing the same will be described with reference to FIGS. GaAs according to this embodiment
As shown in FIG.
Ga composed of a first semiconductor region 1a made of ⁺ type GaAs and a second semiconductor region 1b made of n ⁻ type GaAs
The semiconductor device includes an As semiconductor substrate 2, a Schottky barrier electrode 3 in contact with the second semiconductor region 1b, and a brazing electrode 4 in contact with the first semiconductor region 1.

In accordance with the present invention, the brazing electrode 4
It has a laminated structure of a first layer 5 made of a uGeNi layer, a second layer 6 made of an AuNi layer, a third layer 7 made of a Ni layer, and a fourth layer 8 made of an Au layer. The first
Layer 5 is not always made of only AuGeNi, and is at least partially an alloyed layer with GaAs. However, in FIGS. 1 and 3 to 6, AuGeNi is written on the first layer 5 for easy understanding.

The thickness of each layer is exemplified as follows. The first layer 5 is 0.13 μm, the second layer 6 is 0.5 μm
m, the third layer 7 is 0.5 μm, and the fourth layer 8 is 0.5 μm
It is.

The first layer 5 is a layer for obtaining good ohmic contact with the GaAs semiconductor region 1a as in the first layer of the conventional electrode. The second layer 6 has a third layer 7 thereunder.
Is a layer for preventing Ni from diffusing into the GaAs semiconductor region 1a and preventing erosion by solder from the side.
When Ni diffuses into the GaAs semiconductor region 1a,
Problems such as a decrease in ohmic contact between the semiconductor region 1a and the electrode 4 occur. The third layer 7 is a layer for improving the adhesion to the solder. The fourth layer 8 is the third layer 7
This is a layer for preventing oxidation of and improving solder wettability.

The Schottky barrier diode of FIG. 1 is manufactured as follows. First, the first and second semiconductor regions 1
a, a GaAs semiconductor substrate 2 composed of
AuGeNi and Au are successively deposited on the main surface of the semiconductor region 1a by a well-known vacuum evaporation method, and as shown in FIG.
A uGeNi layer 5a and an Au layer 6a are formed.

Next, the semiconductor substrate 2 having the AuGeNi layer 5a and the Au layer 6a is subjected to a heat treatment at 370-390 ° C. for 10-30 minutes. Thereby, as shown in FIG. 3, the first layer 5 in good ohmic contact with the first semiconductor region 1a is obtained. During this heat treatment, Au
At least a part of the GeNi layer 5a is formed in the first semiconductor region 1
Alloying with GaAs of a, good ohmic contact is obtained. The degree of alloying of the AuGeNi layer 5a with GaAs changes depending on the heating temperature and time, and the entire AuGeNi layer 5a can be an alloyed layer with GaAs. Further, heat treatment can be performed so that alloying of the AuGeNi layer 5a and GaAs does not substantially occur.

Next, Ni and Au are continuously vapor-deposited on the main surface of the Au layer 6a by a well-known vacuum vapor deposition method to form a Ni layer 7a and an Au layer 8a as shown in FIG.

Next, a first layer 5, a first Au layer 6a, N
The semiconductor substrate 2 having the i-layer 7a and the second Au layer 8a is subjected to a heat treatment at about 300 ° C. lower than the first heat treatment temperature for about 60 minutes. Thereby, the A of the first Au layer 6a is
u is alloyed with Ni of the Ni layer 7a to obtain the second layer 6 shown in FIG. 1 and composed of an AuNi alloy layer. Also,
The Ni layer 7a and the Au layer 8a in FIG. 4 become the third layer 7 and the fourth layer 8 shown in FIG.

The first Au layer 6a shown in FIG. 4 is not alloyed with Ni in the entire thickness direction, and the first layer 5 and the second layer 6 made of AuNi are not alloyed as shown in FIG. In some cases, a thin Au layer 6a may remain. Further, a part of the Ni layer 7a and the Au layer 8 shown in FIG.
In some cases, a part of a is alloyed to form an AuNi alloyed layer 9 between the third layer 7 made of Ni and the fourth layer 8 made of Au as shown in FIG.

FIG. 5 shows a state in which the Schottky barrier diode shown in FIG. 1 is fixed to a metal support 10 with lead-tin solder 11. When the solder is interposed between the electrode 4 and the support 10 and heated, the fourth layer 8 made of Au is eroded by the solder 11 and disappears, and the third layer 7 made of Ni comes into contact with the solder 11. . Since the third layer 7 made of Ni is satisfactorily bonded to the solder 11, the support 10 and the electrode 4 are connected to the solder 1.
1 can be firmly bonded. FIG.
As shown in FIG. 3, AuNi is provided between the third layer 7 and the fourth layer 8.
When the layer 9 is interposed, the AuNi layer 9 contacts the solder 11. The AuNi layer 9 can be firmly bonded to the solder 11 like the Ni layer.

According to this embodiment, the following effects can be obtained. (1) When the electrode 4 is fixed to the support 10 by the solder 11, the third layer 7 made of Ni having good solderability after the fourth layer 8 made of Au is eroded by the solder or AuN shown in FIG.
Since the i-layer 9 is exposed and the solder 11 comes in contact therewith, good solder bonding is achieved. (2) The second layer made of AuNi is formed on the first layer 5 containing Ge.
Since the layer 6 is applied, the deposition of Ge on the surface of the electrode 4 is prevented, and the deterioration of the compatibility with the solder can be prevented. Therefore, the solderability is improved in combination with the above (1). (3) Since the second layer 6 made of the AuNi alloy layer is formed by the second heat treatment, erosion of the second layer 6 from the side by the solder 11 can be suppressed. That is, if the Au layer 6a in FIG. 4 is soldered as it is, the Au layer 6a is largely eroded from the side by the solder, but if the second layer 6 is made of AuNi as shown in FIG. And the peeling of the third layer 7 can be prevented. Note that A
In order to convert the u layer 6a to the second layer 6 made of AuNi, the heat treatment temperature is desirably set to 280 ° C. or higher. However, if the heat treatment temperature is too high, Ni becomes GaAs.
Since it diffuses to the semiconductor region 1a, it is preferable to set the temperature to 320 ° C. or lower, which is lower than the first heat treatment temperature. (4) Since the first Au layer 6a is formed relatively thick, it is possible to prevent Ni of the third layer 7 from diffusing to the GaAs semiconductor region 1a. For this purpose the Au layer 6a
Is desirably 3000 Å or more.

[0018]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) The first semiconductor region 1a is not limited to GaAs,
A region containing GaAs as a main component, for example, an AlGaAs semiconductor region can be used. (2) Not limited to Schottky barrier diodes,
The present invention can also be applied to semiconductor devices such as pn junction diodes, FETs, transistors, and light emitting devices.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a Schottky barrier diode according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a semiconductor substrate in which an AuGeNi layer and an Au layer are formed to form the diode of FIG. 1;

FIG. 3 is a cross-sectional view showing a state after heat treatment is performed on the structure shown in FIG. 2;

FIG. 4 is a cross-sectional view showing a structure in which a Ni layer and an Au layer are further formed on the structure shown in FIG. 3;

FIG. 5 is a sectional view showing a state after the diode of FIG. 1 is soldered to a support.

FIG. 6 shows that the Au layer remains between the first and second layers,
FIG. 11 is a cross-sectional view showing a diode in which an AuNi layer is formed between a fourth layer and a fourth layer.

[Explanation of symbols]

 1a first semiconductor region 4 electrode 5 first layer 6 second layer 7 third layer 8 fourth layer 11 solder

Claims (6)

[Claims] 1. A semiconductor device comprising: a semiconductor substrate having a semiconductor region made of GaAs (gallium arsenide) or a compound semiconductor containing Ga and As as a main component; and an electrode in ohmic contact with the semiconductor region. A first layer including AuGeNi (gold / germanium / nickel) disposed adjacent to the semiconductor region; and a second layer including AuNi (gold / nickel) disposed adjacent to the first layer. A third layer of Ni (nickel) disposed adjacent to the second layer; and a fourth layer of Au (gold) disposed adjacent to the third layer.
Wherein the first, second, third, and fourth layers are sequentially stacked. 2. The semiconductor device according to claim 1, wherein the first layer is a layer including at least a part of an alloyed layer of AuGeNi and a semiconductor material of the semiconductor region. 3. The method according to claim 1, wherein an A is provided between the first layer and the second layer.
3. The semiconductor device according to claim 1, wherein a u (gold) layer is interposed. 4. A layer between the third layer and the fourth layer.
4. The semiconductor device according to claim 1, wherein a uNi (gold / nickel) layer is interposed. 5. GaAs (gallium arsenide) or Ga and A
a semiconductor substrate having a semiconductor region composed of a compound semiconductor containing s as a main component, and a method for forming the electrode in a semiconductor element having an electrode in contact with the semiconductor region, wherein a main surface of the semiconductor region is provided. Forming an AuGeNi layer by depositing AuGeNi on the first layer, and depositing Au on the surface of the AuGeNi layer to form a first A layer.
forming a u-layer; heat-treating a semiconductor substrate having the AuGeNi layer and the first Au layer; forming a Ni layer by depositing Ni on a surface of the first Au layer Forming a second Au layer by depositing Au on the surface of the Ni layer; and forming the AuGeNi layer, the first Au layer, the Ni layer, and the second Au layer. Subjecting the semiconductor substrate to heat treatment so as to alloy a part of the Ni layer with at least a part of the first Au layer to obtain an AuNi layer. Method. 6. The step of forming the AuGeNi layer and the step of forming the first Au layer comprise AuGeNi and Au.
Wherein the step of forming the Ni layer and the step of forming the second Au layer are steps of continuously depositing Ni and Au. Item 6. The electrode forming method according to Item 5.