JPH05315595A - Compound semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a compound semiconductor device from deteriorating in ohmic contact properties and Schottky contact properties due to the diffusion of metal atom by a method wherein various metal atoms of electrode material are prevented from diffusing into the substrate by a carbon layer provided between a compound semiconductor substrate and an electrode. CONSTITUTION:A carbon layer 12 is formed on a GaAs substrate 11, and a W layer 13 of a conductive layer is laminated thereon. The carbon layer 12 is formed through a sputtering method, and the W layer 13 is laminated through a sputtering method. After the lamination of the W layer 13, the GaAs substrate 11 is subjected to a RTA treatment to enable carbon atom to move to the position of As atom contained in the GaAs substrate 11. Furthermore, a metal wiring is formed on the surface of the GaAs substrate 11. By this setup, the carbon layer 12 functions as a barrier between the GaAs substrate 11 and the W layer 13, and even if the GaAs substrate 11 is exposed to an atmosphere of high temperature in a manufacturing process, W atoms are prevented from diffusing in the GaAs substrate 11. Therefore, a compound semiconductor device is enhanced in reliability of electrical properties and kept low in resistivity and high in thermal stability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor device, and more particularly to a compound semiconductor device used for Schottky gate field effect transistors, heterojunction bipolar transistors and the like.

[0002]

2. Description of the Related Art Conventionally commonly used GaAs and Al
Substituting Ga, Al and In atoms contained in the substrate as a p-type electrode on a GaAs and InGaAs semiconductor substrate
A group II element Zn, Mg, Be layer and the like were laminated. FIG. 3 shows an example of such a compound semiconductor device. Zn, which is a group II element, is vapor-deposited on a p-type GaAs substrate 1 at low pressure by a method such as resistance heating, electron beam heating, or sputtering. Forming layer 2. Then, by the same method, the Au layer 3 is laminated on the Zn layer to form the p-type ohmic contact on the compound semiconductor substrate.

FIG. 4 also shows an example of a conventional compound semiconductor device, in which a Ti layer 5, a Pt layer 6 and an Au layer 7 are laminated on an n-type GaAs substrate 4 in the same manner as described above to form a compound. A Schottky contact is formed on the semiconductor substrate.

[0004]

In such a conventional compound semiconductor device, the manufacturing process is often carried out at a high temperature, which makes it possible to use the electrode material at the contact portion between the compound semiconductor substrate and the electrode. There is a problem that the ohmic contact property and the Schottky contact property are deteriorated by mixing and permeating a certain metal into the compound semiconductor substrate.

In particular, p-type metal atoms diffuse very quickly into the compound semiconductor substrate due to heat treatment at high temperature.
When the compound semiconductor substrate is processed at a high temperature, the ohmic contact property and the Schottky contact property are often lost, and the same problem occurs in a thin compound semiconductor device such as a bipolar transistor.

[0006]

In order to solve the above problems, according to the present invention, there is provided a compound semiconductor device having an electrode formed of at least one conductive layer on a compound semiconductor substrate. An electrode is formed by sequentially stacking a carbon layer and a conductive layer thereon, or a first conductive layer and a carbon layer are sequentially formed on the compound semiconductor substrate, and a second conductive layer is further formed on the carbon layer. There is provided a compound semiconductor device in which electrodes are formed by stacking.

The compound semiconductor substrate in the present invention is mainly
III-V group compounds, specifically GaAs, AlGa
Examples include As and InGaAs. The electrode formed on the compound semiconductor substrate may be composed of one conductive layer, or may be composed of two conductive layers or more conductive layers stacked. In this case, the conductive layer forming the electrode is formed of a common metal such as W, Zn or A.
u, AuGeNi, Al, Ti / Pt / Au, Al / T
i / Pt / Au, Ti / Pt, etc. can be used. These electrodes can be formed by a known method such as resistance heating, electron beam heating, or sputtering.

The carbon layer formed on the compound semiconductor substrate or the conductive layer in the present invention is formed by a known method such as a sputtering method or an electron beam evaporation method, and its thickness is preferably about 10 to 50 nm.

[0009]

According to the above structure, a compound semiconductor device having an electrode formed of at least one conductive layer on a compound semiconductor substrate, wherein a carbon layer and a conductive layer are sequentially laminated on the compound semiconductor substrate. Or the first conductive layer and the carbon layer are sequentially formed on the compound semiconductor substrate, and the second conductive layer is further laminated on the carbon layer to form the electrode. The carbon layer provided between the compound semiconductor substrate and the electrode acts as a thermally stable barrier that prevents diffusion of metal atoms, which are various electrode materials, into the substrate. That is, the diffusion coefficient of carbon into a compound semiconductor substrate is usually
Since it is much lower than that of the group element, it prevents diffusion of metal atoms, which are electrode materials, into the compound semiconductor substrate, and prevents deterioration of ohmic contact property and Schottky contact property due to diffusion. In addition, carbon partially substitutes the constituent atoms of the compound semiconductor substrate and acts as an acceptor in the crystal of the p-type compound semiconductor substrate, thereby reducing the resistance of the contact portion between the compound semiconductor substrate and the electrode. Becomes

[0010]

EXAMPLE An example of a compound semiconductor device according to the present invention will be described with reference to FIGS. FIG. 1 shows an example of a compound semiconductor device using a carbon layer 12 in a contact portion showing p-type ohmic characteristics. In FIG. 1, 11 is a p-type GaAs substrate which is a compound semiconductor substrate, a carbon layer 12 is formed on the GaAs substrate 11, and a W layer 13 which is a conductive layer is further laminated.

The carbon layer 12 was formed with a film thickness of about 30 nm by the sputtering method, and the W layer 13 was further laminated on the carbon layer 12 with a film thickness of about 200 nm by the sputtering method. After stacking, RTA (Rapid Thermal Aneal) treatment was performed for 10 seconds at a temperature of about 600 to 900 ° C. so that carbon atoms were moved to As atom sites in the GaAs substrate 11. Further, although not shown, a compound semiconductor device is completed by forming metal wiring on the surface of the GaAs substrate 11.

In the compound semiconductor device having such a structure,
The carbon layer 12 acts as a barrier between the GaAs substrate 11 and the W layer 13, and can prevent W atoms from diffusing into the GaAs substrate 11 even if the GaAs substrate 11 is exposed to high temperature in the manufacturing process. Further, in FIG. 2, the carbon layer 16 is used in the contact portion showing the Schottky characteristic,
2 shows a compound semiconductor device showing a second embodiment of the present invention.

In the figure, 14 is an n-type GaAs substrate which is a compound semiconductor substrate, and a Ti layer 15, a carbon layer 16 and an Au layer 17 which are electrodes are laminated on the GaAs substrate 14. These Ti layer 15, carbon layer 16 and Au layer 1
7 has a thickness of about 10 nm for the Ti layer 15, about 30 nm for the carbon layer 16 and about 200 nm for the Au layer 17 formed by the general method of low pressure vapor deposition as in Example 1.

Further, as in the first embodiment, this GaAs
The compound semiconductor device is completed by forming metal wiring on the surface of the substrate 14. In the semiconductor device having such a structure, the presence of the carbon layer 16 causes the Au atoms in the Au layer 17 to become G
It can be prevented from diffusing into the aAs substrate 14.

[0015]

As described above, the compound semiconductor device of the present invention is a compound semiconductor device in which an electrode made of at least one conductive layer is formed on the compound semiconductor substrate, and the compound semiconductor device is provided on the compound semiconductor substrate. To form an electrode by sequentially stacking a carbon layer and a conductive layer, or sequentially forming a first conductive layer and a carbon layer on the compound semiconductor substrate, and further forming a second conductive layer on the carbon layer. Since the electrodes are formed by stacking, the carbon layer provided between the compound semiconductor substrate and the electrode can prevent diffusion of metal atoms, which are various electrode materials, into the substrate, and is thermally stable. Acts as a barrier. That is, the diffusion coefficient of carbon into the compound semiconductor substrate is usually injected into the substrate as an impurity.
Since it is much lower than Group II elements, it is possible to prevent the diffusion of metal atoms, which are the electrode material, into the compound semiconductor substrate, and to prevent the ohmic contact property and the Schottky contact property from being deteriorated due to the diffusion. Also, especially p
In the crystal of the type compound semiconductor substrate, carbon partially replaces the constituent atoms of the compound semiconductor substrate and acts as an acceptor, so that the resistance of the contact portion between the compound semiconductor substrate and the electrode can be reduced.

Therefore, the reliability of the electrical characteristics of the compound semiconductor device is high, low resistance and thermal stability can be realized, and the contact portion of an ultra-thin compound semiconductor device such as a bipolar transistor can be formed.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a main part showing an embodiment of an ohmic contact part of a compound semiconductor device of the present invention.

FIG. 2 is a schematic cross-sectional view of an essential part showing an embodiment of the Schottky contact part of the compound semiconductor device of the present invention.

FIG. 3 is a schematic cross-sectional view of a main part showing an embodiment of an ohmic contact part of a conventional compound semiconductor device.

FIG. 4 is a schematic cross-sectional view of a main part showing an embodiment of a Schottky contact part of a conventional compound semiconductor device.

[Explanation of symbols]

 11 p-type GaAs substrate (compound semiconductor substrate) 12, 16 carbon layer 13 W layer (conductive layer) 14 n-type GaAs substrate (compound semiconductor substrate) 15 Ti layer (first conductive layer) 17 Au layer (second conductivity) layer)

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location H01L 29/73 21/338 29/812 7376-4M H01L 29/80 M

Claims (1)

[Claims] 1. A compound semiconductor device having an electrode formed of at least one conductive layer on a compound semiconductor substrate, wherein a carbon layer and a conductive layer are sequentially laminated on the compound semiconductor substrate to form an electrode. Or a first conductive layer and a carbon layer are sequentially formed on the compound semiconductor substrate, and a second conductive layer is further laminated on the carbon layer to form an electrode. Semiconductor device.