JPS6232656A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain an element having excellent high frequency characteristics, by providing a very thin layer, which includes a material, whose bonding strength with oxygen is higher than any of a semiconductor substrate and a high melting point metal thin film, between the semiconductor substrate and the high melting point metal thin film. CONSTITUTION:On one main surface of a semi-insulating substrate 1, an N-type active layer 2 is formed by using a selective ion implanting technology. Then, by using a magnetron sputtering method, Si and W are sequentially deposited. An electrode is machinged by a dry etching technology using CF4+O2. Then heat treatment is performed. Thereafter, gold (Au)-germanium (Ge) (12wt% Ge is included) is deposited by an electron beam evaporation method to a thickness of about 1,500Angstrom . Nickel (Ni) is deposited by the same evaporation method to a thickness of about 500Angstrom . Electrodes are machined by a liftoff method. Then, heat treatment is performed in argon (Ar) bubbles for one minute, and a source electrode 6 and a drain electrode 7 are formed. Thus the gate electrode characterized by low resistance and high heat resistance in comparison with a conventional technology can be implemented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a compound semiconductor device and a method for manufacturing the same. Especially high melting point metals? I! The present invention relates to a compound semiconductor device having a film as a gate electrode and a method for manufacturing the same.

(Summary of the Invention) The present invention provides a semiconductor device having a high melting point metal thin film on one main surface of a semiconductor substrate, in which the semiconductor substrate and the high melting point metal thin film are disposed between the semiconductor substrate and the high melting point metal thin film. By having an intermediate layer with a thickness of 2 to 100 A made of a material with a stronger bonding force with oxygen than either of these, it is possible to create a semiconductor device having a gate electrode made of a high melting point metal thin film with low resistivity and high heat resistance. 0 Also, in the method of manufacturing a semiconductor device according to the present invention, which includes a step of depositing a high melting point metal thin film on one main surface of a semiconductor substrate, the high melting point metal thin film ['(z) is deposited as an intermediate layer before being deposited. Sputtering method.

Silicon (St) by either evaporation method or vapor phase growth method
An object of the present invention is to provide a method for manufacturing a semiconductor device having a gate electrode made of a high melting point metal thin film having low resistivity and high heat resistance by e-deposition.

(Prior art and problems to be solved by the invention) In recent years,
In communication in high frequency bands of several GHz or higher, friend elements using compound semiconductors, such as gallium arsenide (GaAs), are attracting attention. In particular, elements with high-melting point metal thin 11iffi gate electrodes are attracting attention due to the simplicity of the manufacturing process. is attracting attention and research and development is being actively carried out.

Taking a gallium arsenide (GaAs) Schottky gate field effect transistor as an example, the conventional refractory metal thin 1li
FIG. 3 shows a cross-sectional view of the main part of a semiconductor device having I as a gate electrode. In Fig. 3, 1 is a semi-insulating substrate, 2
is an n-type active layer, and an n+ region 3.4 is provided in the source/drain region to reduce series resistance. 5
is a Schottky gate electrode, 6 is a source electrode, and 7 is a drain electrode.

Conventionally, in the Schottky gate electrode 5 made of a high melting point metal thin film, a high melting point metal compound such as tungsten silicide (WSiz) or a single high melting point metal thin film such as tungsten CW) deposited directly on the entire semiconductor surface has been used. It was getting worse. However, high melting point metal compounds, such as WSi
At t, the heat resistance of the electrical characteristics of the junction with the semiconductor surface is high, but the resistivity is as high as 100 μΩ·σ or more, which has the disadvantage of causing an increase in the noise figure in the high frequency characteristics. For this reason, it is necessary to lower the sheet resistance, but increasing the film thickness has been difficult due to manufacturing constraints such as poor processability. Although a single high-melting point metal such as W has a low resistivity of about 10 μΩ·G, it has problems with adhesion to the surface of a semiconductor substrate and heat resistance of electrical properties.

(Friendly Means to Solve All Problems) An object of the present invention is to provide a semiconductor device having a gate electrode made of a high melting point metal thin film with low resistivity and high heat resistance, which solves these drawbacks, and a method for manufacturing the same. There is a particular thing.

Most preferably, the semiconductor device according to the present invention has an extremely thin layer between the semiconductor substrate and the high melting point metal thin film that contains a substance having a stronger bonding force with oxygen than either the semiconductor substrate or the high melting point metal thin film. Main characteristics.

Whether the substance has a stronger bonding force with oxygen than either a semiconductor substrate, such as a gallium arsenide (GaAs) substrate, or a high melting point metal thin film, such as tungsten (W), can be determined from the oxide formation energy. .

For example, Ga.

The oxide formation energies of As + W and Si are approximately -80 Kcal and -46 per mole of oxygen atoms, respectively.
Kcal.

-60 Kcal and -100 Kcal, which shows that Si easily combines with Ikko oxygen.

The function of the electrode film according to the present invention will be explained in comparison with that of a conventional electrode film using a high melting point compound such as metal silicide in terms of resistance and heat resistance.

In terms of resistance, in the present invention, the thickness of the sandwiched intermediate layer is extremely thin, less than 100 Å, and the resistance of this part can be ignored compared to the total film thickness (200 Å). It provides low resistance equivalent to that of high melting point metals.

In addition, as for heat resistance, both are equivalent, so in terms of resistance and heat resistance, the present invention is equivalent to using a single high melting point compound.

(Example) Figure 1 shows an example of the present invention.
s) is a diagram illustrating a field effect transistor,
In the figure, 1 is a semi-insulating substrate, 2 is an n-type active layer, 3, 4
teeth? Area 5 is tungsten (W) with a film thickness of approximately 200OA.
The thin film 5' is an extremely thin layer mainly composed of silicon (Si), 6 is a source electrode, and 7 is a drain electrode.

In order to realize this structure, in the embodiment of FIG.
Just do it like this. An n-type active layer 2 is formed on one main surface of a semi-insulating substrate 1 using a selective ion implantation technique. Next, using the magnetron sputtering method, St
+ W f sequentially deposited. It is processed into an electrode by dry etching technology using CF4 + Ot 't', and then heat treated. Thereafter, gold (Au)-germanium (Ge) (containing 12 wt% of Get) is etched at about 150O
A, Approximately 500'A of nickel (Ni) was sequentially deposited using the electron beam evaporation method, processed into an electrode by the lift-off method, and then heated at 450°C in an argon (Ar) bubble.
.

Heat treatment is performed for 1 minute, and the source electrode 6. It is assumed to be a drain electrode 7. As described above, the structure of the present invention can be easily formed using known processes.

When the thickness of the Si layer is changed in the range of 0-5OA,
The Schottky barrier height and ideality factor of the above example after heat treatment by lamp annealing for several seconds at 100°C were
As shown in the figure. The Schottky barrier height and ideality factor are determined by a known method from the current-voltage characteristics of the Schottky barrier diode. Therefore, the closer the ideality factor is to 1, the more ideal the Schottky junction is. here the second
As shown in the figure, when a Si layer of approximately 15 A is sandwiched, the /Yottky junction characteristics are improved. Mayu, S.
When the thickness of the i layer exceeds 100 A k, wH and GaAs
A W silicide layer is generated at the interface with the substrate, causing volumetric contraction and causing film peeling. Moreover, even if it is too thin, such as 2A or less, sufficient effects of the Si layer cannot be obtained. Si
If the thickness of the layer is within the range of 2〃. There is no problem even if the Si layer reacts with oxygen or W[1 to form a compound.

As is clear from the above results, the present invention can realize a gate electrode having lower resistance and higher heat resistance than conventional techniques.

Note that as an intermediate layer made of a substance that has a stronger bonding force with oxygen than either the semiconductor substrate or the high melting point metal thin film, Vi,
Table 1 (Effects of the Invention) As explained above, according to the present invention, a semiconductor device having an electrode of a refractory metal thin film having low resistance and high heat resistance. can be realized.

It has the advantage of excellent high frequency characteristics and can be used as a companion element.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of one embodiment of the device of the present invention, FIG. 2 is a diagram showing the relationship between Si layer thickness, Schottky barrier height, and ideality factor for explaining the present invention, and FIG. 3 is a diagram of the conventional device. 01 showing a cross-sectional view of a compound semiconductor device having a gate electrode made of a high melting point metal thin film... Semi-insulating substrate 2
・・・・・・・・・・・・N-type active layer 3.4・・・・・・
・Female region 5... Schottky gate electrode 5
′......Extremely thin layer 6 whose main component is silicon...Source electrode 7.
・・・・・・・・・Drain electrode No. 1 Fig. 3 Fig. 2 Si layer (destruction (A)

Claims (3)

[Claims] (1) In a semiconductor device having a high melting point metal thin film on one main surface of a semiconductor substrate, there is a greater amount of oxygen between the semiconductor substrate and the high melting point metal thin film than in either the semiconductor substrate or the high melting point metal thin film. A semiconductor device characterized by having an intermediate layer with a thickness of 2 to 100 angstroms made of a material with a large bonding force. (2) The semiconductor device according to claim 1, wherein the intermediate layer is made of a material containing at least silicon (Si). (3) In a method for manufacturing a semiconductor device including a step of depositing a high melting point metal thin film on one main surface of a semiconductor substrate, before depositing the high melting point metal thin film, an intermediate layer is formed by sputtering, vapor deposition, or vapor deposition. A method for manufacturing a semiconductor device, comprising depositing silicon (Si) by one of phase growth methods.