JPH0513448A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a highly reliable semiconductor device and to increase the yield at the time of manufacture of the device by a method wherein the characteristics of the interface between a surface protective film and a compound semiconductor layer are stabilized. CONSTITUTION:A semiconductor device is characterized in that it has a plurality of electrodes 4, 5 and 6 formed on the surface of a compound semiconductor layer 3, a silicon layer 7 formed on the semiconductor layer 3 surface between the electrodes 4, 5 and an insulating film 8 formed on the layer 7.

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 field effect transistor or a Schottky diode using a compound semiconductor, and more particularly to a semiconductor device having a highly reliable surface protective film.

[0002]

2. Description of the Related Art As a conventional semiconductor device in which a Schottky contact is formed on a compound semiconductor, there is, for example, a Schottky barrier type high frequency GaAs field effect transistor (hereinafter referred to as GaAs MESFET) or a GaAs Schottky diode. In these semiconductor devices, a silicon dioxide (SiO ₂ ) film, a silicon nitride (Si ₃ N ₄ ) film is used as a surface protective film of GaAs which is a compound semiconductor.
A film or a multilayer structure film thereof is used.

[0003]

In compound semiconductors such as GaAs, a good surface protective film such as a combination of Si and SiO ₂ films has not yet been found. For this reason,
SiO ₂ film or Si as a surface protection film on the compound semiconductor
_In a conventional semiconductor device in which only an insulating film such as a ₃ N ₄ film is formed, the interface between the surface protective film and the compound semiconductor is unstable.
Therefore, the conventional semiconductor device has the following problems due to the instability of the interface between the surface protective film and the compound semiconductor. That is, in the GaAs MESFET, the leakage current between the gate electrode / source electrode and between the gate electrode / drain electrode increases, and the interface current changes due to the leakage current flowing, and the Schottky characteristic of the gate electrode deteriorates. Also, there is a problem that the breakdown voltage between the gate electrode and the source electrode and the drain electrode is deteriorated, and the reliability in long-time operation is lowered. Further, in the GaAs Schottky diode, there is a problem that the leak current between the Schottky electrode and the ohmic electrode increases and the breakdown characteristic becomes soft. Further, these semiconductor devices have a problem in that the variations in characteristics on the wafer surface at the time of manufacturing become large and the yield decreases.

Therefore, it is an object of the present invention to provide a semiconductor device having stable interface characteristics between a surface protective film and a compound semiconductor and high reliability, and a high yield at the time of manufacturing.

[0005]

In order to solve the above-mentioned problems, firstly, the present invention provides a compound semiconductor, a plurality of electrodes formed on the surface of the compound semiconductor, and the above-mentioned between the plurality of electrodes. It is a gist to have a silicon layer formed on the surface of a compound semiconductor and an insulating film formed on the silicon layer.

Secondly, the gist of the first structure is that the plurality of electrodes formed on the surface of the compound semiconductor form a Schottky barrier field effect transistor.

The third and first configurations are summarized in that a plurality of electrodes formed on the surface of the compound semiconductor form a Schottky diode.

Preferably, GaAs is used as the compound semiconductor.
III-V group compound semiconductors such as

The silicon layer is made of an amorphous or polycrystalline material and has a thickness of about 50 to 1000 angstroms. The method for forming the silicon layer does not damage the compound semiconductor surface.
For example, a vacuum vapor deposition method or the like is desirable. Further, an n-type or p-type impurity may be doped to the extent that it does not affect the operation of the semiconductor device.

[0010]

In the above structure, firstly, the deterioration of breakdown voltage between the plurality of electrodes is considered to be caused by the electric field concentration on the surface of the compound semiconductor. The present invention is based on the idea of stabilizing the interface in order to reduce the electric field concentration on the surface of the compound semiconductor. By using the silicon layer at this interface, mutual diffusion with the compound semiconductor is reduced.
Thermodynamically stable at the interface with the compound semiconductor and no chemical reaction occurs. Natural oxide film of compound semiconductor (S
reduce heat of formation less than iO ₂ (eg Ga
₂ O ₃ and As ₂ O ₃ have a smaller heat of formation than SiO ₂ .
In addition, by applying a low temperature forming method, for example, a vacuum vapor deposition method as a method of forming the silicon layer, it becomes possible to prevent decomposition of the compound semiconductor surface portion. Therefore,
Stable interface characteristics can be obtained.

Since stable interface characteristics can be obtained, the second
In the Schottky barrier type field effect transistor,
The Schottky characteristic of the gate electrode and the breakdown voltage between the gate electrode and the source and drain electrodes are prevented from being deteriorated.

Thirdly, in the Schottky diode, the leakage current between the Schottky electrode and the ohmic electrode is reduced and a steep breakdown characteristic is obtained.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are views showing a first embodiment of the present invention. This embodiment is applied to GaAs MESFET.

First, referring to FIG. 1, a GaAs MESFET
The structure will be described. On the semi-insulating GaAs substrate 1, a non-doped GaAs layer 2 as a buffer layer and an n-type GaAs layer 3 as an operating layer are formed by a vapor phase epitaxial growth method.
Are sequentially stacked to form a compound semiconductor substrate portion 10. The non-doped GaAs layer 2 has a thickness of about 2 μm, and the n-type GaAs layer 3 is Si-doped and has a carrier concentration of 3 × 10 ¹⁷ cm.
^-3 , and the thickness is about 0.15 μm. The AuGe / Ni /
The source electrode 4 and the drain electrode 5 having a multilayer structure of Au are formed by ohmic contact. A recess is formed in the substrate portion 10 between the source electrode 4 and the drain electrode 5, and the n-type GaAs layer 3 and the gate electrode 6 having a Ti / Al laminated structure forming a Schottky barrier are formed in the recess portion. ing.

On the surface of the substrate portion 10, a two-layer structure film of a silicon layer 7 and a SiN film 8 is formed as a GaAs surface protection film. The silicon layer 7 is formed to a thickness of about 100 Å by the electron beam evaporation method, and the SiN film 8 is formed by the plasma CVD method at the substrate temperature 2
It is formed to a thickness of about 600 Å at 50 ° C. Portions of the source electrode 4 and the drain electrode 5 are opened in the surface protective films 7 and 8, and bonding pads (not shown) are formed in the opened portions.

Ga of this embodiment constructed as described above
Since the silicon layer 7 is formed on the GaAs surface and the Si / GaAs interface is stable in the AsMESFET, stable interface characteristics can be obtained without outward diffusion of Ga atoms during the subsequent manufacturing process or FET operation. This prevents the breakdown voltage between the gate electrode 6, the source electrode 4, and the drain electrode 5 from being deteriorated.

FIG. 2 shows changes with time in breakdown breakdown voltage between the gate and the drain when a current of 1.8 mA / mm is passed between the gate electrode and the drain electrode to accelerate deterioration. Here, the breakdown withstand voltage is defined as the voltage between the gate electrode and the drain electrode when a current of 36 μA / mm flows between the gate electrode and the drain electrode. In FIG. 2, the initial value breakdown breakdown voltage is 15 V, the a characteristic line is the characteristic of this embodiment, and the b characteristic line is the GaAs MESF using only the SiN film as the surface protection film as a comparative example.
The characteristic of ET is shown. From the characteristics shown in the figure, the breakdown withstand voltage of this example hardly changes with time, and the breakdown voltage is significantly prevented from being deteriorated as compared with the comparative example.

Next, FIGS. 3 and 4 show a second embodiment of the present invention. This embodiment is applied to a GaAs Schottky diode.

In FIG. 3, members which are the same as or equivalent to the members and the like in FIG. 1 are designated by the same reference numerals as those used above, and duplicate explanations are omitted.

In this embodiment, A is formed on the n-type GaAs layer 3.
An ohmic electrode 11 having a multilayer structure of uGe / Ni / Au is formed. At a position separated from the ohmic electrode 11 by about 3 μm, a Schottky electrode 12 having a laminated structure of Ti / Al / Ti forming an n-type GaAs layer 3 and a Schottky barrier is formed. The size of the Schottky electrode 12 is 280 μm in width and 0.5 μm in length.
It is about m.

FIG. 4 shows GaAs constructed as described above.
The reverse direction characteristic of the Schottky diode (characteristic line a) is shown. The b characteristic line is the characteristic of the GaAs Schottky diode in which only the SiN film is used as the surface protection film as a comparative example. It is clear from the characteristics of the figure that the breakdown characteristics of this example are steep. Also, in Table 1, 2
The breakdown voltage and leakage current average and dispersion of about 500 Schottky diodes manufactured on an inch GaAs wafer are shown.

[0023]

[Table 1]

From the table, the breakdown voltage of this example is about 4 V higher and the variation is about 1 V smaller than the comparative example. Furthermore, the leak current is reduced by one digit or more. Therefore, it is clear that a high yield can be obtained during manufacturing.

In each of the above embodiments, the GaAs FET is used.
However, the present invention is not limited to this and is also applicable to a semiconductor device using InP or a semiconductor device such as a heterojunction FET based on InP.GaAs. it can. Further, although the silicon nitride film is used as the insulating film in the embodiment, a dense insulating film such as a silicon oxide film may be used.

[0026]

As described above, according to the present invention,
First, the silicon layer is formed on the surface of the compound semiconductor between the plurality of electrodes, and the insulating film is formed on the silicon layer. Therefore, the silicon / compound semiconductor interface is thermodynamically stable and has a stable interface with little mutual diffusion. The characteristics can be obtained. Therefore, it is possible to prevent the breakdown voltage and the like between the plurality of electrodes from being deteriorated, and it is possible to remarkably improve the reliability.
In addition, at the time of manufacturing, variations in characteristics within the wafer surface are reduced, and a high yield can be obtained.

Since the stable interface characteristics are obtained as described above, secondly, in the structure of the Schottky barrier field effect transistor, the Schottky characteristic of the gate electrode is deteriorated and the gate electrode, the source electrode and the drain electrode are deteriorated. It is possible to prevent the breakdown voltage between them from deteriorating.

Thirdly, in the structure of the Schottky diode, the leakage current between the Schottky electrode and the ohmic electrode is reduced and a steep breakdown characteristic can be obtained.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment of a semiconductor device according to the present invention.

FIG. 2 is a characteristic diagram showing a change with time in breakdown breakdown voltage between the gate and the drain of the first embodiment together with a comparative example.

FIG. 3 is a vertical sectional view showing a second embodiment of the present invention.

FIG. 4 is a diagram showing reverse characteristics of the second embodiment together with a comparative example.

[Explanation of symbols]

4 Source electrode 5 drain electrode 6 Gate electrode 7 Silicon layer 8 SiN film 10 Compound semiconductor substrate 11 Ohmic electrode 12 Schottky electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location H01L 23/31 29/48 H 7738-4M 29/76 8422-4M 29/784 8225-4M H01L 29 / 78 301 B

Claims (3)

[Claims] 1. A compound semiconductor, a plurality of electrodes formed on the surface of the compound semiconductor, a silicon layer formed on the surface of the compound semiconductor between the plurality of electrodes, and a silicon layer formed on the silicon layer. A semiconductor device having an insulating film. 2. The semiconductor device according to claim 1, wherein the plurality of electrodes formed on the surface of the compound semiconductor form a Schottky barrier field effect transistor. 3. The semiconductor device according to claim 1, wherein the plurality of electrodes formed on the surface of the compound semiconductor form a Schottky diode.