JPH06120163A - Forming of electrode of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain good ohmic characteristics as well as deposit characteristics in the forming of an ohmic contact electrode on the surface of a crystal comprising III-V compound semiconductors including Al by treating the crystal surface by sputtering in a vacuum device and eliminating oxides. CONSTITUTION:Ga on the surface of a GaAlAs layer, which is formed on top of a semiconductor insulating substrate 1 comprising GaAs, is first removed, and an oxide formed on the surface of the GaAlAs layer 2 is removed by reverse sputtering in normal high frequency in a vacuum device. Next, N side electrode 8 is formed by normal sputtering. For electrode material, any materials will suffice so long as it provides ohmic contact for GaAlAs of the N type. In this instant, after reverse sputtering, by sputtering the next electrode material in the same vacuum device, the GaAlAs surface which has been exposed during the sputtering can form an electrode material on a clean surface without being in touch with the oxidation atmosphere. Subsequently, it is subjected to a few minutes of heat treatment in a nitrogen atmosphere.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming electrodes on a semiconductor device, and more particularly to a method for forming electrodes on the surface of a III-V compound semiconductor substrate containing Al.

2. Description of the Related Art In recent years, various devices such as light emitting diodes, semiconductor lasers, field effect transistors, and photodiodes, which take advantage of the characteristics of III-V group compound semiconductors, have been put into practical use, and their fields of application have been expanding. However, the physical properties of these compound semiconductor materials change in a complicated manner in the element manufacturing process as compared with a single element material such as Si, and the element manufacturing process is often not simple and requires high technology. In particular, the surface of the compound semiconductor containing Al is unstable and is likely to change due to heat treatment or chemical treatment during manufacturing, and there is a problem that it is difficult to form an electrode for ohmic contact. In response to this, various measures have been studied. FIG. 3 is an explanatory diagram of an electrode forming method disclosed in Japanese Patent Laid-Open No. 56-16619, which is one of the conventional examples. According to this method, first, Ga
Te doping (n≈5 to 10 × 10 ¹⁷ cm ⁻³ ) on the semiconductor insulating substrate 1 made of As by the liquid phase epitaxial method.
N-type Ga _(1-X) Al _X As layer (x ≈ 0.8 to 0.9)
2 is grown to a thickness of 40 to 50 μm. After that, Ga is heated to a temperature higher than 200 ° C. by using an ordinary vacuum deposition method.
A method of forming the AuGeNi electrode 3 on the AlAs surface is used. In addition, FIG. 4 is another example of a conventional example (LR Zheng et al .: Applied Phys.
icsLetter. Vol. 60, No. 7, p. 8
77-879 (1992)) is an explanatory view of the electrode forming method disclosed in FIG. According to this method, first, Se-doped (n≈7.5 × 10 ¹⁷ cm ⁻³ ) N-type Ga _(1−X) Al is formed on the semiconductor insulating substrate 1 made of GaAs by the liquid phase epitaxial method. _X As layer (x≈0.55) 2 thickness 200
nm growth. Next, the surface of the GaAlAs layer is sequentially treated with ammonia-perhydrogen-based and hydrofluoric acid-nitric acid-based chemicals, and then the Pd layer 4 and AuG are formed using a normal vacuum deposition method.
The e layer 5, the Ag layer 6, and the Au layer 7 are laminated to form an electrode. After that, 400 ℃ -500 ℃ under nitrogen atmosphere, 3
A method of heat treatment under the condition of 0 seconds is used.

As mentioned above, Ga
The AlAs surface is active, and an oxide film is usually formed by the surrounding atmosphere. Therefore, the electrode is formed after the oxide film is removed by chemical treatment. However, the exposed crystal surface after the oxide film is removed is also easily activated and oxidized. G up to a vacuum device that performs water washing treatment, drying treatment and electrode formation according to chemical treatment
An oxide film is newly formed on the GaAlAs surface due to the ambient atmosphere even during handling of the aAlAs substrate. In the above-mentioned conventional example, the oxide film is destroyed to adhere the electrode metal to the crystal surface to obtain sufficient adhesion and good ohmic contact. However, since this oxide film has a thickness of about 1 nm to 10 nm and the thickness is not uniform, it is difficult to obtain a uniform ohmic contact in a fine region even by these methods. That is,
For example, in a fine circular electrode having an electrode diameter of several tens of μm or less, rectification is seen in voltage-current characteristics, and there is a problem that the resistance of the electrode also varies. Therefore, when manufacturing a device such as an LED array that requires fine size electrodes, GaAl
In some cases, GaAs is formed on As and the electrode is brought into contact with GaAs. However, especially in such a light emitting device, this method is not sufficiently satisfactory at present because GaAs serves as an absorber of the emitted light.

The present invention has been made in view of the above problems, and the invention according to claim 1 is
“In the formation of an ohmic contact electrode on the surface of a crystal made of a III-V group compound semiconductor containing Al, the surface of the crystal is treated by a sputtering method in a vacuum apparatus to remove oxides, and then the crystal is removed. An electrode forming method for a semiconductor device, characterized in that an electrode material for obtaining ohmic contact is formed on the surface of the crystal without taking it out from the vacuum device. "
According to a second aspect of the invention, in the method for forming an electrode of a semiconductor device according to the first aspect, the electrode material is 200 ° C. or higher and 550 ° C.
A method of manufacturing a semiconductor device, which comprises forming on a crystal surface at the following temperature. Is provided.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a semiconductor device for explaining an electrode forming method for a semiconductor device according to a first embodiment of the present invention. In the figure, reference numeral 1 is a semiconductor insulating substrate made of GaAs, and reference numeral 2 is Te-doped (n≈1 × 10 ¹⁸ cm ⁻³ ) N-type formed on the semiconductor insulating substrate 1 by a liquid phase epitaxial method to a thickness of 10 μm. Ga _(1−X) Al _X As
It is a layer (x≈0.7). First, Ga on the surface of the GaAlAs layer 2 is removed, and the oxide formed on the surface of the GaAlAs layer 2 is removed by a normal high frequency reverse sputtering method in a vacuum device (not shown). Reverse sputtering conditions are reverse sputtering pressure of 2 Pa and reverse sputtering power of 100.
W. Next, the N-side electrode 8 is formed by the usual sputtering method. The electrode material is Au-Ge (12 wt%)-Ni
(4 wt%), which are circular with a diameter of 10 μm and are linearly arranged at intervals of 200 μm. Any electrode material may be used as long as it allows ohmic contact with N-type GaAlAs. After reverse sputtering here,
By sputtering the next electrode material in the same vacuum apparatus, the exposed GaAlAs surface does not come into contact with the oxidizing atmosphere and the electrode material can be formed on a clean surface. After that, 400 ℃ -500 ℃ in nitrogen atmosphere
Heat treatment is performed for several minutes in an electric furnace maintained at. This is performed for the purpose of alloying the electrode material and the semiconductor to obtain ohmic contact. The heat treatment may be performed in the same vacuum device immediately after sputtering the electrode material. If the latter method is used, there is a possibility that it will occur between the electrode formation and the heat treatment.
There is no need to worry about As surface oxidation. As described above, N
It is possible to form the electrode 8 having good ohmic characteristics and adhesion characteristics with respect to the GaAlAs of the mold. In the above-described first embodiment, the N electrode is formed on the N-type GaAlAs, but even when the conductivity type is the P-type, the P-type GaA is used.
It can be applied by using an electrode material capable of obtaining ohmic contact with lAs. FIG. 2 is a sectional view of a semiconductor device for explaining an electrode forming method of the semiconductor device according to the second embodiment of the present invention. First, a metalorganic vapor phase epitaxial method (MOCVD) is applied on a semiconductor insulating substrate 1 made of GaAs.
Method, Zn-doped (n≈5 × 10 ¹⁷ cm ⁻³ ) P-type G
A _(1−X) Al _X As layer (x≈0.45) 2 is formed to a thickness of 2 μm. On the other hand, after performing reverse sputtering similar to that of the first embodiment to remove the oxide on the surface of the GaAlAs layer 2,
The P-side electrode 9 is formed on the surface of the GaAlAs layer 2 set at 300 ° C. by a normal sputtering method in the same vacuum apparatus. The electrode material is Au-Be (1 wt%). However,
Any electrode material may be used as long as it can obtain ohmic contact with P-type GaAlAs. The temperature at this time is 200 ° C. or lower, and the voltage-current characteristic shows rectifying property, and at 550 ° C. or higher, A is observed from the GaAlAs crystal surface.
It is necessary to be in the range of 200 ° C. or higher and 550 ° C. or lower because s is desorbed and defects are induced to cause crystal deterioration. In this way, the GaAlAs crystal surface is kept at 200 ° C.
When the electrode material is formed while maintaining the temperature above 550 ° C.,
Since the alloying reaction between the electrode material and the semiconductor occurs at the same time when the electrode material is deposited and ohmic contact is obtained, the heat treatment by the electric furnace or the like performed in the first embodiment is unnecessary. In addition, there is a possibility that GaAlAs due to oxygen that has entered through pinholes or the like of the electrode material that may occur between electrode formation and heat treatment.
No need to worry about oxidation of the surface. As described above, the electrode 9 having good ohmic characteristics and adhesion characteristics with respect to the P-type GaAlAs can be formed. In the second embodiment described above, formation of the P electrode on the P-type GaAlAs is shown. However, even when the conductivity type is N-type, N-type GaAlA
It can be applied by using an electrode material capable of obtaining ohmic contact with s. In the first and second embodiments described above, G
Although aAlAs is used, the same effect can be obtained by applying it to another III-V group compound semiconductor containing Al. In addition to the above-described embodiments, the present invention can be applied to the fabrication of semiconductor devices, such as light emitting diodes, laser diodes, and hetero bipolar transistors, which require the formation of ohmic electrodes in III-V group compound semiconductors containing Al. Is something that can be done.

As described above, according to the method for forming an electrode of a semiconductor device of the present invention, an ohmic electrode can be extremely easily formed on a crystal plane of a III-V group compound semiconductor containing Al. Further, since the effect of oxidation on the crystal surface can be sufficiently eliminated, the ohmic contact becomes uniform, and even if an electrode having a small area is formed, good ohmic characteristics and adhesion characteristics can be obtained, and variations in electrode resistance are reduced.
These improve the productivity and reliability of the electrode.
Furthermore, the oxide film on the crystal surface is removed by the reverse sputtering method, and then the electrode material is formed, eliminating the need for complicated pretreatments such as complicated chemicals for removing the oxide film, which is conventionally required. It can be realized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor device for explaining an electrode forming method for a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor device for explaining an electrode forming method of the semiconductor device according to the second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a conventional electrode forming method.

FIG. 4 is an explanatory diagram of another conventional electrode forming method.

[Explanation of symbols]

 1 Semiconductor Insulating Substrate 2 GaAlAs Layer 3 AuGeNi Electrode 4 Pd Layer 5 AuGe Layer 6 Ag Layer 7 Au Layer 8 Electrode 9 Electrode

Claims (2)

[Claims] 1. Forming an ohmic contact electrode on the surface of a crystal composed of a III-V group compound semiconductor containing Al,
A method of forming an electrode material for obtaining ohmic contact on the surface of the crystal without removing the crystal from the inside of the vacuum apparatus after treating the surface of the crystal by a sputtering method in a vacuum apparatus to remove oxides. Method for forming electrode of semiconductor device. 2. A method for manufacturing a semiconductor device according to claim 1, wherein the electrode material is formed on the crystal surface at a temperature of 200 ° C. or higher and 550 ° C. or lower.