JPS5845831B2 - Method for manufacturing a shotgun barrier semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a Schottky barrier semiconductor device having improved characteristics.

A PN junction semiconductor device that utilizes conduction of minority carriers accumulates minority carriers during switching operations, and cannot be adapted to high-speed switching.

On the other hand, Schottky barrier semiconductor devices, which utilize an energy barrier formed on the semiconductor surface by contact between a metal and a semiconductor, use conduction of majority carriers, so there is no accumulation of minority carriers, and high-speed switching is possible. Can adapt.

Therefore, Schottky barrier semiconductor devices, especially diodes, are used for detection, mixing, and switching in the UHF band or microwave band.

In addition, the Schottky barrier element has a forward voltage drop of PN.
It has the advantage of being smaller than that of a bonding element.

However, it also has the drawback of low reverse breakdown voltage.

As shown in FIG. 1, in a Schottky barrier diode in which a metal layer 3 such as chromium is provided on a silicon substrate in which an N-type silicon layer 2 is evixively grown on a fiN+-type silicon layer 1, when a reverse voltage is applied, the metal layer 3 and The electric field is concentrated at the periphery of contact with the N-type silicon layer 2, and breakdown generally occurs in this area.

In order to solve this drawback, as shown in FIG. 2, a P-type silicon region 4 may be provided at the periphery of the contact between the metal layer 3 and the N-type silicon layer 2 to form a guard ring.

In FIG. 2, 5 is a silicon oxide film.

If the guard ring structure is used as described above, the reverse breakdown voltage will certainly increase.

However, since the PN junction formed between the P-type silicon region 6 and the N-type silicon layer 2 is also used, the switching characteristics deteriorate.

In addition, in order to form the P+ type silicon region 6 deeply, the N
It is necessary to increase the thickness of the shaped silicon layer 2,
The drawback was that the forward voltage increased.

In order to improve the reverse direction characteristics, as shown in FIG. 3, the metal layer 3 can be covered with the silicon oxide film 5 to form a field plate shape to prevent concentration of the electric field at the periphery. It has been impossible to expect sufficient effects due to restrictions on the impurity concentration of semiconductors.

Further, as shown in FIG. 4, an alloy layer of silicon and metal, that is, a silicide layer 6, may be formed by heat-treating an N-type silicon layer 2 with a metal layer 3 deposited thereon.

In this way, the height of the energy barrier, that is, the barrier bite becomes high, and the reverse breakdown voltage value also becomes high.

However, there was a drawback that forward voltage and power loss were increased.

In order to solve this kind of problem, it is conceivable to make the height of the energy barrier lower in the center and higher in the periphery.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method that can easily form a Schottky barrier semiconductor device in which a portion with a low energy barrier is surrounded by a portion with a high energy barrier.

To achieve the above object, the present invention includes a step of forming a thin silicon oxide film on a part of a silicon semiconductor substrate, and a metal layer on the surface of the silicon semiconductor substrate on the silicon oxide film and surrounding the silicon oxide film. a step of forming;
A method for manufacturing a Schottky barrier semiconductor device, comprising the step of heating so that the energy barrier between the semiconductor substrate and the metal layer is low in the region where the silicon oxide film is formed and high in the region surrounding the silicon oxide film. It is related to.

According to the present invention, it is possible to form a portion with a low energy barrier simply by providing a silicon oxide film, so it is possible to easily provide a Schottky barrier semiconductor device in which a portion with a low energy barrier is surrounded by a portion with a high energy barrier. I can do it.

Since the reverse breakdown voltage is determined primarily by the high energy barrier portion and the forward voltage is determined primarily by the low energy barrier portion, an ideal Schottky barrier semiconductor device can be provided.

Next, embodiments of the present invention will be described based on the drawings.

5 to 12 relate to the first embodiment of the present invention.

The Schottky barrier element is shown in the order of manufacturing steps.

In this embodiment, first, as shown in FIG. 5, an N-type silicon layer 12 with a specific resistance of 0.1 to 1.0 Ω is placed on top of an N-type silicon layer 11 with a specific resistance of 0.005 Ω. 5-10
Epitaxially grown to a thickness of approximately 200 μm.
of the silicon substrate, and the upper surface of the N-type silicon layer 12 has a
An oxide film 13 having a thickness of 1,000 people was formed.

Next, as shown in FIG. 6, an opening 14 was formed leaving a portion of the oxide film 13.

Next, the silicon substrate is boiled with a mixture of ammonia and hydrogen peroxide to remove the N exposed through the opening 14.
About 10 hydrophilic silicon oxide films 15 were formed on the shaped silicon layer 12 as shown in FIG.

The thin silicon oxide film 15 formed by this treatment is a hydrophilic film containing 10H groups.

Next, the peripheral portion of the thin silicon oxide film 15 is removed by photo-etching, and an opening 16 is formed as shown in the cross-sectional view of FIG. 8 and the plan view of FIG. 11, and the thin silicon oxide film 15 is shaped like an island. left.

Next, after cleaning the surface, as shown in FIG. 9, a chromium layer 17 is deposited on the thin silicon oxide film 15 and the N-type silicon layer 12 in the opening 16 to a thickness of about 3,000 mm using a vacuum evaporation method. Ta.

Next, heat treatment was performed at 450° C. for 30 minutes in a nitrogen atmosphere.

As a result, in the portion where the N-type silicon layer 12 and the chromium layer 17 are in direct contact, an alloy layer of chromium and silicon, that is, a chromium silicide layer 18, as shown in FIG.
was formed.

On the other hand, chromium silicide was not formed in the area where the thin silicon oxide film 15 was provided.

As a result, as shown in FIG. 12, a Schottky barrier element having a shape in which a portion 19 where chromium silicide is not formed is surrounded by a portion 20 where chromium silicide is formed is completed.

The barrier bite φBn in the portion 20 of this element is 0.
65 eV, and the barrier bite φBn in part 19
is 0.55 eV, and when a forward voltage is applied, the lower part of the barrier bite19
Most of the forward current flowed through.

This is because even though the silicon oxide film 15 is interposed between the chromium layer 17 and the N-type silicon layer 12 in the portion 19,
This is thought to be because the silicon oxide film 15 is extremely thin, about 10λ, and electrons pass through it due to the tunnel effect.

Therefore, the forward voltage and power loss of this Schottky barrier element were smaller than those in which the silicide layer 6 was formed over the entire surface as shown in FIG.

In addition, the reverse breakdown voltage is as shown in FIG.
It had almost the same size as the one that formed it.

This is because the silicide layer 18 is formed at the peripheral edge and the barrier bite is increased.

13 and 14 show a second embodiment of the present invention, in which a Schottky barrier is formed through a plurality of thin silicon oxide films 15 surrounded by a chromium silicide layer 18. is provided.

Even in this case, the same effect as the first embodiment can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and can be further modified.

For example, other metals may be used in place of chromium.

Moreover, although the thin silicon oxide film 15 was formed by boiling with a mixture of ammonia and hydrogen peroxide, this boiling may be performed with aqua regia or sulfuric acid.

Alternatively, the silicon oxide film 15 may be formed by a thermal oxidation method.

However, in any case, 5 to 20A is preferable.

Further, in the first, second, and third embodiments, the silicide layer is not formed in the portion surrounded by the chromium silicide layer 18, but it is formed so thin that it does not affect the forward characteristics. Even in such a case, the object of the present invention can be achieved.

[Brief explanation of the drawing]

1, 2, 3, and 4 are cross-sectional views showing conventional Schottky barrier elements, and FIG. 5, FIG. 6, and FIG.
8, 9, and 10 are cross-sectional views showing the Schottky barrier element according to the first embodiment of the present invention in the order of manufacturing steps, and FIG. 11 is a plan view in the state shown in FIG. 8. 12th
10 is a plan view of the state shown in FIG. 10, FIG. 13 is a plan view showing a second embodiment of the present invention, and FIG. 14 is a sectional view taken along the line A--A in FIG. 13. In the reference numbers used in the drawings, 12 is an N-type silicon layer, 15 is a thin silicon oxide film, 16 is an opening, and 17 is a thin silicon oxide film.
is a chromium layer, and 18 is a chromium silicide layer.

Claims (1)

[Claims] 1. A step of forming a thin silicon oxide film on a part of a silicon semiconductor substrate, and a step of forming a metal layer on the surface of the silicon semiconductor substrate surrounding the silicon oxide film and the silicon oxide film. and a step of heating so that the energy barrier between the semiconductor substrate and the metal layer is low in the region where the silicon oxide film is formed and high in the region surrounding the silicon oxide film. manufacturing method.