JPH0212017B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gallium arsenide semiconductor device,
In particular, this device contains gallium arsenide (hereinafter referred to as gallium arsenide)
This relates to the electrode structure of field-effect transistors (referred to as GaAs).

GaAs field-effect transistors are increasingly being used in microwave equipment due to their excellent high frequency and characteristics. Furthermore, research and development of microwave monolithic integrated circuits and high-speed logic elements including GaAs field-effect transistors has begun to be actively conducted.

Figure 1 shows a typical structure of a GaAs field effect transistor that has been used in the past. In this example, on an active region 2 formed on a semi-insulating substrate 1, source/drain ohmic electrodes 3 and 4 made of an alloy of gold/germanium, silver/indium/germanium, etc. and a shot gate 5 made of aluminum etc. are provided. It consists of the following basic structure.
A gold layer 7 is usually formed on the ohmic electrodes 3 and 4 via a high melting point metal layer 6 such as molybdenum, tantalum, or a titanium-platinum laminated layer so that bonding can be easily performed. Further, a gold layer 10 is also formed on the bonding portion 8 of the shot gate metal via a high melting point metal layer 9 of the same type as the source and drain portions. The reason why the gate bonding part is also structured like this is that even if the same gold bonding wire used to connect the source and drain electrodes is used to connect the gate electrode, it prevents the reaction between the gate metal aluminum and the gold wire. Therefore, this is to prevent deterioration of the element.

The reason behind the adoption of this structure is that GaAs
In order to form a good ohmic electrode, there is no other way than to use an alloy contact method based on gold or silver, and for this reason, it is necessary to standardize the source and drain electrode metals to gold-based metals. , so to speak, has been treated as an inevitable technology unique to compound semiconductors centered on GaAs. However, in this conventional electrode structure, a multilayer metal electrode structure is used for all of the source, drain, and gate electrodes, which is structurally complex and requires that all electrodes be made of gold. This results in an increase in the cost of device manufacturing materials, and is one of the obstacles to lowering the price of GaAs devices. Furthermore, when the field effect transistor having the structure mentioned in this example is applied to an integrated circuit, a gold-based metal is also used for wiring such as connection between elements, which leads to further increase in material cost. Further, a gold wire is used for bonding to the gold-based electrode, and a thermocompression bonding method is used for bonding. Bonding using thermocompression bonding requires strict temperature control to prevent deterioration of the source, drain, and gate electrodes, as well as to ensure a stable connection between the electrodes and wires, and the bonding index time is also shorter than that of silicon. It has the disadvantage of being slower than the aluminum wiring commonly used in devices. The present invention eliminates the major drawbacks and provides an improved gallium arsenide semiconductor device, that is, semi-insulating.
A GaAs field effect transistor formed on a GaAs substrate has its source and drain electrodes formed of an alloy layer containing a component metal of gold or silver, and a high melting point metal layer provided so as to overlap at least a portion of this alloy layer. and an aluminum layer provided so as to overlap at least a portion of the high melting point metal layer.

An embodiment of the present invention will be described below with reference to FIG.

The use of a material in which the active region is formed on the semi-insulating GaAs substrate 11 is the same as in the conventional case. The source and drain ohmic electrodes 13 and 14 are
Gold/germanium, silver/indium/germanium, silver/tin or gold/germanium/nickel, etc.
It is formed from an alloy containing gold or silver, or a metal group containing an alloy. A high melting point metal layer or a combination layer 15 of high melting point metals made of tantalum, tungsten, molybdenum, etc., or a laminated platinum-titanium layer is formed so as to overlap at least a portion of this alloy layer. Furthermore, an aluminum layer 16 is formed on the high melting point metal layer 15. The gate electrode 17 is made of a metal whose surface is aluminum, such as aluminum, a titanium-aluminum lamination, a tantalum-aluminum lamination, or the like.

In the GaAs field effect transistor of this structural example, an aluminum wire can be used as a bonding wire, and the bonding speed can be increased using a device similar to that used for bonding silicon devices. In addition, since gold-based electrodes are not used as in the past, manufacturing material costs can be reduced. When such field-effect semiconductor devices are used to manufacture microwave monolithic integrated circuits and high-speed logic integrated circuits that include GaAs field-effect transistors, all impedance matching lines and connection lines between elements are standardized to aluminum lines. The effect of reducing the cost of manufactured materials becomes more noticeable.

Furthermore, the GaAs semiconductor device of the present invention is shown in FIG. 3 and has additional advantages as described below. That is, by making the uppermost layer of all electrodes uniformly made of aluminum, the aluminum 26 on the source and drain and the aluminum of the upper layer 272 of the gate electrode 27 , in this example, can be formed at the same time. or a high melting point metal layer, such as tantalum.
Aluminum laminated structure for source and drain
5, 26, and the lower layer 271 and upper layer 272 of the gate 27 can be formed simultaneously, which simplifies the element formation process and contributes to lower costs.

Although the above embodiments have been described using a shot gate field effect transistor as an example, the present invention can be similarly applied to an insulated gate field effect transistor and a semiconductor device including the same. Furthermore, although several examples of electrode constituent metals are listed, the present invention is not limited to these, and other combinations may also be selected. If the basic electrode structure includes an alloy layer, a high melting point metal layer, and an aluminum layer, it is also possible to select a more multilayered structure, for example, a modified structure such as gold/germanium-gold-molybdenum-aluminum.

According to this invention, it is possible to easily bond the transistor, reduce the cost of the material, simplify the element structure, shorten the element formation process, and maintain high performance. Contains GaAs field effect transistors
It has the advantage of being able to provide GaAs semiconductor devices at a lower price than before.

[Brief explanation of drawings]

FIG. 1 is a top view showing the structure of a conventional field effect transistor, FIG. 2 is a top view showing the structure of a field effect transistor of the present invention, and FIG. 3 is a top view of another field effect transistor of the present invention. FIG. 3 is a cross-sectional view showing an example structure. 2 and 3, 11, 21... semi-insulating substrate, 12, 22... active region, 13, 23... source alloy layer, 14, 24... drain alloy layer, 1
5, 25... High melting point metal layer, 16, 26... Aluminum layer, 17, 27 ... Gate electrode metal, 2
72...Aluminum layer, 271...High melting point metal layer.

Claims (1)

[Claims] 1. A gallium arsenide field effect transistor formed on a semi-insulating gallium arsenide substrate has its source and drain electrodes overlapped with an alloy layer containing a component metal of gold or silver, and at least a portion of this alloy layer. 1. A gallium arsenide semiconductor device comprising a high melting point metal layer and an aluminum layer provided to overlap at least a portion of the high melting point metal layer.