JPS5845832B2 - Kinzoku-Handoutai Seiriyuseisetsugouno Seihou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a stable and high quality metal-semiconductor rectifying junction with good reproducibility using an alloy reaction of gallium arsenide (GaAs) and platinum (Pt).

Conventionally, the rectifying junction obtained by depositing metallic platinum on n-type gallium arsenide has a barrier
It is often used because of its high Height), but
It is known that there are various drawbacks regarding its reliability.

Particularly for power devices whose joints tend to reach high temperatures during use, an alloying reaction between platinum and gallium arsenide may occur during operation, resulting in changes in properties, or other metals such as gold ( If gold (Au) or the like is attached, there are problems such as not only a reaction between platinum and gallium arsenide but also the fact that the gold in the upper layer passes through the platinum layer and reaches gallium arsenide, causing a change in device characteristics.

In Japanese Patent Publication No. 50-24189 (hereinafter referred to as Cited Example (1)), which was distributed before the application of the present application, n-type G a A
A PT layer is formed on the surface of the s crystal and heat treated to form Pi and GaA.
It is described that a Schottky barrier is formed by providing an alloy layer of S.

In addition, JP-A-50-108878, which was filed before the filing date of the present application and published after the filing date of the present application (hereinafter referred to as (2)
) describes a method of vacuum-depositing Pt and W (or Mo) in this order on the surface of an n-type GaAs crystal while heating it.

The difference in structure between the cited example (1) and the present application is that W is not attached to the surface.

In actual devices, electrodes such as Au are attached on top of the alloy layer for operation.

Between Au and the alloy layer (without W, Au passes through the alloy layer and reaches GaAs due to the temperature increase due to operation, changing the device characteristics.

At the same time, Ga escapes from the system due to the temperature rise.

Ga is supplied from GaAs to compensate for this shortage of Ga.

Then, the position of the interface between PtAs and GaAs changes.

In devices such as invat diodes, where the impurity profile below the interface must be precisely designed, the electrical characteristics deteriorate.

It is stated on page 2 of the specification and attached drawing Figure 3 of Cited Example (1) that the characteristics of the Schottky barrier diode were good and that there was no deterioration in breakdown voltage in the reliability test, but if In the reliability test, the characteristics deteriorate due to the above-mentioned omission of Ga.

Reference example (2) differs from the present application in that heat treatment is performed before attaching W to the surface.

In other words, in the cited example (2), GaAs and Pt are reacted by heating the GaAs crystal and depositing Pt, and then W, Mo, etc. are deposited, and W2MO is used for metals used for electrodes (e.g. Au, etc.). ) and GaAs reacted with platinum.

In this case, as we saw in our experiments, part of the Ga in the GaAs that participated in the reaction disappears out of the system during the reaction process, and the layer structure of PtGa/PtAs2/GaAs in the strict sense is not established. .

More detailed description is as follows. In Example 1 of Cited Example (2), only 10 times more Pt was deposited on the GaAs crystal using a normal vacuum deposition method.

If it is this thin, PT will not form a perfect film.

Therefore, Mo formed thereon comes into direct contact with GaAs.

Therefore, a good Schottky barrier cannot be formed.

In other words, it seems that this first embodiment is not practical.

Next, Example 2 of the cited work by Isa will be described.

If Pt is attached to a GaAs crystal without heating it at 300°C, Ga will escape from the system, so it will not be just PtGa (Pt5G 33 etc., a phase lacking in Ga will be mixed with PtGa and formed). .

After this, W was attached on top.

During the deposition of W, P' t 5 Ga 3 tries to become PtGa and sucks out Ga from GaAs, so As becomes excessive in PtAs2, and the strict PtA
It does not become s2, but becomes an As-excess phase (herein written as PtAs2*).

Moreover, PtAs2 and PtGa (Pt5Ga3) are not clearly separated as layers, but are in a mixed state.

Thereafter, a heat treatment of 450'C1H2 for 5 minutes was performed to form Au and finally to completely react Pt and GaAs.

However, even in this case, there is still an excess of As, so the layer structure of PtGa/PtAs2/GaAs cannot be obtained.

As a result, even if formed as a diode, P t A 52
The interface between * and GaAs gradually reacts, resulting in P t A 52
As * tries to become PtAs2ζ, As moves.

However, since As cannot escape from the system due to the presence of W, it is difficult to form P t A s2 in the strict sense.

In the end, the method of Example 2 results in stable P t Ga/P t
A layered structure called s2/GaAs cannot be created.

As a result, when a Schottky barrier diode is operated for a long time, its barrier bite and n value of the diode deteriorate.

It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a method for producing metal-semiconductor rectifying junctions of a structure that is stable even when operated at high temperatures. Platinum (Pi) with a thickness of 500X or more and 3000X or less is deposited on gallium (n-GaAs), and tungsten (W) with a thickness of 500X or more and 5000A or less is further deposited on top of that, and the whole is heat treated. A metal-semiconductor rectifying junction characterized in that the platinum layer is completely reacted with a part of the gallium arsenide substrate to change the structure to gallium arsenide-platinum arsenide-platinum gallium-tungsten (GaAs/PtAs2/PtGa/W). A manufacturing method is obtained.

According to the present invention, a stable and high quality rectifying joint can be obtained.

In other words, the contact between gallium arsenide and platinum arsenide is 0.9 eV.
Gallium arsenide and platinum arsenide each have a high potential barrier and are metallurgically stable compounds, so even if they are allowed to coexist, no reaction will occur even if they are heated to a temperature of about 700'C.

In addition, even if platinum arsenide and platinum gallium are coexisting, no reaction occurs under similar conditions, and platinum gallium itself is a stable compound.

Second, tungsten is a metal that is stable even at high temperatures, and even if it coexists with platinum gallium, platinum, gold, or others, it will not react under similar conditions.

Therefore, a thermally extremely stable metal-semiconductor rectifying junction is obtained.

The present invention will be described in detail below using an example.

50% each of platinum and tungsten was deposited using a general vacuum evaporation method on a sample piece of n-type gallium arsenide that had been pretreated using a conventional method.
Deposit to 0X and 1000X thickness.

Next, this sample piece is heat treated at 450° C. for 10 minutes in a hydrogen atmosphere to form a rectifying junction.

Thereafter, about 1000X of gold germanium (AuGe) is attached to the back surface of the sample piece, and a resistive contact is made by heat treatment at 450° C. for 1 minute in a hydrogen atmosphere.

The thus obtained sample piece is cut into an appropriate size and chemically etched to complete a rectifying element (diode).

The devices obtained in this way are extremely stable; for example, even after high-temperature storage at 500°C for 200 hours, no change in properties was observed, making them far superior to bonded devices obtained by conventional methods. It was confirmed that it was heat resistant.

Controlling the thickness of platinum and tungsten is extremely important here.

In other words, if it is too faint, it may be a so-called pinhole.
On the other hand, if the temperature is too high, a large stress (5 tres
s), and in some cases, the alloy layer etc. may peel off and the element may be damaged.

Furthermore, even if this does not occur, the electrical characteristics of the element deteriorate due to internal stress.

Although the present invention has been described above using examples, the thickness of platinum and tungsten is arbitrary within the range shown in the claims, and the heat treatment temperature, time, etc. can be determined as appropriate depending on the thickness of platinum. A more stable bond can be obtained.

Claims (1)

[Claims] 1 Platinum (Pt) with a thickness of 500X or more and 3000X or less is attached to the surface of n-type gallium arsenide (GaAs), and tungsten (W) with a thickness of 500X or more and 5oooX or less is further attached on top of it, and the whole is heat-treated. By this, the platinum layer is completely reacted with a part of the gallium arsenide to form gallium arsenide-platinum arsenide-platinum gallium-tungsten (GaA
A method for manufacturing a metal-semiconductor rectifying junction, characterized by forming a structure such as s/PtAs2PtGa-W).