JPH02185041A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form a metallic layer or an insulating layer excellently onto the top face of an S thin-layer by shaping the S(sulfur) thin-layer onto the surface of a semiconductor base body having a compound semiconductor region using Ga(gallium) as one main component and forming a coating layer onto the top face of the thin-layer under the state in which the semiconductor base body is cooled. CONSTITUTION:A thin-layer 3 composed of S is shaped onto the surface of a compound semiconductor region 2 in a semiconductor base body 1 having the compound semiconductor region 2 employing Ga as one main component, and a coating layer 4 is formed onto the top face of the thin-layer 3 under the state in which the semiconductor base body 1 is cooled. Consequently, sine the coating layer 4 is shaped under the state in which the semiconductor base body 1 is cooled, S atoms dissociating from the surface of the compound semiconductor region 2 are decreased. When the coating layer 4 consists of a metallic layer, the coating layer 4 is formed extremely thinly, and converted into a metallic oxide layer through oxidation, thus forming structure in which the compound semiconductor region 2 is covered with an insulator. Accordingly, the coating layer can be formed onto the S thin-layer shaped onto the surface of the compound semiconductor region without substantially damaging the surface stabilizing effect of the S thin-layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for forming a monoatomic layer of S (sulfur) on the surface of a semiconductor substrate having a compound semiconductor region containing Ga (gallium) as a main component. The present invention relates to a method of manufacturing a semiconductor device in which a covering layer is formed through a thin layer of.

Problems to be solved by recent techniques and inventions The surface of GaAs (gallium arsenide) has a unique instability.
This is one reason why the commercialization of semiconductor devices has not progressed as expected. Also regarding the Schottky barrier (metal-semiconductor rectifying barrier) formed on the compound semiconductor region made of GaAs.

It has been difficult to form a Schottky barrier having a desired barrier hydride or to form a Schottky barrier with a small reverse current with good reproducibility.

On the other hand, the inventors of the present application have discovered that n-type GaAg-5iOzllll
(Silicon oxide film) -AQ In a MIS (metal-insulator-semiconductor) structure consisting of an (aluminum) electrode system, by treating the GaAs surface with an ammonium sulfide solution, a thin S layer at a monoatomic layer level is formed on the GaAs surface. It has been found that good MIS characteristics can be obtained by forming a . In addition, for Schottky barrier structures made of n-type GaAs-AQ electrodes, etc., good Schottky barrier properties can be obtained by treating the GaAs surface with an ammonium sulfide solution to form a thin S (sulfur) layer on the GaAs surface. I found it. In addition, these research results were presented at the 20th Isohedral Elements and Materials Conference (sponsored by the Japan Society of Applied Physics).
Held from August 24th to 26th, 1988), etc.

However, since the S thin layer is extremely thin, on the order of a monoatomic layer or two atomic layers, the S of the S thin layer is formed by Ga A during the process of forming a metal layer and an insulating layer on the top surface of the S thin layer. It may dissociate from the S surface, and the surface stabilizing effect of the S thin layer may be impaired.

Accordingly, one object of the present invention is to provide a method for manufacturing a semiconductor device, which solves the above problems and allows a metal layer or an insulating layer to be satisfactorily formed on the upper surface of the S thin layer.

In the method for manufacturing a semiconductor device according to the present invention for the purpose of Thereafter, a coating layer is formed on the upper surface of the thin layer while the semiconductor substrate is cooled.

Further, in the method for manufacturing a semiconductor device according to the present invention, after forming the first insulating layer by oxidizing the covering layer made of metal, the second insulating layer is further formed on the upper surface of the first insulating layer.

The above-mentioned coating layer has a thickness of 150 until the layer thickness reaches 10.
It is formed by vacuum evaporation in a cooled state to a temperature below .degree. Further, the layer thickness of the coating layer made of metal to be converted into the first insulating layer is formed to be 300 Å or less.

Production - November 1st The coating layer is formed while the semiconductor substrate is cooled, so
S atoms dissociated from the surface of the compound semiconductor region are reduced. When the covering layer is a metal layer, if the covering layer is formed very thin and then oxidized to convert into a metal oxide layer, a structure in which the compound semiconductor region is covered with an insulator can be formed. Of course, the covering layer can remain as a metal layer and be used as part of a semiconductor structure to form a Schottky barrier and an ohmic contact. When the covering layer is an insulating layer.

It can be used as is for surface stabilization structures and MIS structures using coating layers.

EXAMPLE 1 As an example of the method for manufacturing a semiconductor device according to the present invention, a method for forming a Schottky barrier will be described with reference to FIGS. 1 and 2.

First, as shown in FIG. 1(A), an n
a semiconductor substrate (1) comprising a shaped compound semiconductor region (2),
H,5O4 (sulfuric acid) -Hxon (hydrogen peroxide) -
An etching solution consisting of H and O (water) and an aqueous solution of ammonium sulfide at a concentration of 1N kept at room temperature are prepared.

The impurity concentration of the compound semiconductor region (2) is approximately 5×1101
sa″″3. Ammonium sulfide has the chemical formula (NH
4) a About 8% S relative to the standard compound represented by S
Specifically, the chemical formula: (NH,), Sx
It is ammonium sulfide represented by (x=1.08).

Note that it is desirable that X≧1.02.

Next, the surface of the compound semiconductor region (2) is lightly etched and cleaned with a solution consisting of H, 5O1 (sulfuric acid)-H,O, (hydrogen peroxide)-Hio (water).

The cleaned semiconductor substrate (1) is immersed in the ammonium sulfide solution. The immersion time can be selected from a wide range of seconds to several hours. The semiconductor substrate (1) is taken out of the ammonium sulfide solution, and N, (nitrogen) gas is blown onto the surface of the compound semiconductor region (2) to remove the adhering solution. As a result, the surface of the compound semiconductor region (2) is coated with an amorphous film having a thickness of approximately 10 nm (100 nm) and containing S as a main component. Subsequently, the semiconductor substrate (1) was placed in a vacuum (in a reduced pressure atmosphere) for about 30 minutes.
When left for a minute, this amorphous film almost disappears. As shown in FIG. 1(B), a thin S layer (3) bonded to Ga and As is formed on the surface of the obtained compound semiconductor region (2). According to observation by Auger electron spectroscopy, S in the S thin layer (3), which constitutes ammonium sulfide, is adsorbed on the GaAs surface and remains in the extremely thin layer of about a monoatomic layer or a diatomic layer. Note that in order to obtain the S thin layer (3), other suitable methods may be employed, such as dipping the ammonium sulfide solution and then rapidly diluting this solution with pure water.

Furthermore, using an ultra-high vacuum type vacuum evaporation apparatus schematically shown in FIG. 2, a Sw layer (
3) A metal layer (coating layer) (4) made of AΩ is provided on the upper surface to form a Schottky barrier.
5), a support stand (6) with a built-in heater for temperature adjustment (not shown), a refrigerant container (7) adjacent to the support stand (6), and a refrigerant container (7) connected to the refrigerant container (7). Introductory path (8)
and a discharge channel (9), and a boat-shaped evaporation dish (10).

and an electron gun (11). Support stand (6) and container (
7) constitute a cooler (13).

When forming the metal layer (4), the S shown in FIG.
One main surface of the semiconductor substrate (1) having a thin layer (3) [S
The semiconductor substrate (1) is mounted on the support base (6) with the main surface on which the thin layer (3) is formed facing the evaporation dish (10). The pressure inside the Pelger (5) is reduced to more than I x 10'' Torr, and the /l plate material (12) serving as the evaporation source for forming the metal layer (4) is placed in the boat-shaped evaporation dish (10). In this embodiment, in order to form the metal layer (4) in a cooled state of the semiconductor substrate (1), a support stand (6) is attached to the refrigerant container (7).Introduction Road (
When liquid nitrogen is introduced into the container (7) through the support base (6), the semiconductor substrate (
1) is cooled to a low temperature of -100°C or lower, for example about -150°C. In this state, the surface of the AQ plate material (12) is heated by the electron beam irradiated from the electron gun (11).

AΩ evaporated from the AQ plate material (12) adheres to the upper surface of the S thin layer (3). Note that the nitrogen gas vaporized within the container (7) is discharged to the outside of the vacuum evaporation apparatus through the discharge path (9). Further, the temperature of the semiconductor substrate (1) is mainly controlled by a heater (not shown) built into the support base (6).

Through the above steps, a metal layer (4) with a thickness of approximately 2 μm is formed on the upper surface of the S thin layer (3), and a Schottky barrier is formed between the metal layer (4) and the compound semiconductor region (2). In addition,
In FIG. 1(C), the S thin layer (3) is depicted as existing as it is in the state shown in FIG. 1(B) for convenience, but the S thin layer (
3) is an extremely thin film, so it is not clear in what form the S thin layer (3) actually exists in the state shown in FIG. 1(C).

In this example, cooling of the semiconductor substrate (1) during vacuum deposition reduces the dissociation of S atoms deposited on the surface of the compound semiconductor region (2), and the thin S layer (3) reduces the dissociation of S atoms deposited on the surface of the compound semiconductor region (2). ) The surface stabilizing effect is well and reliably exhibited.

Therefore, barrier hide φbn has a value (φbn40.4aV) that relatively faithfully reflects the work function of AJ,
Furthermore, a Schottky barrier with a small reverse current can be formed.

Next, as a second embodiment of the present invention, a method for forming an MIS structure will be described with reference to FIG.

First, in the same manner as in Example 1, a semiconductor substrate (1) with an extremely thin S thin layer (3) formed on the surface of a compound semiconductor region (2).
), as shown in Figure 3(A), a thin S layer (
3) A metal layer (coating layer) (21) made of AI is formed on the upper surface. Similarly to Example 1, the metal layer (21) is formed by vacuum evaporating All on the semiconductor substrate (1) while cooling it to a low temperature of -ioo°C or lower, for example, about -150°C. However, in Example 2, the layer thickness of the metal layer (21) is
There are only about 100 people, which is significantly thinner than the previous year.

Next, as shown in FIG. 3(B), the semiconductor substrate (1) shown in FIG. 3(A) on which the metal layer (21) has been formed is heated to a temperature of about 350° C. in air. .

The metal layer (21) is thermally oxidized. As a result, the metal layer (2
1) is changed to a metal oxide layer (22) made of an insulator (AQsOsC aluminum oxide) as the first insulating layer. In the thermal oxidation step, since the metal layer (21) is formed in close contact with the upper surface of the S thin layer (3), the SR element is not substantially dissociated from the surface of the compound semiconductor region (2) by heating.

Therefore, the surface stabilizing effect of the S thin layer (3) is not impaired.

Next, as shown in FIG. 3(C), a metal oxide layer (22
) on the top surface of the well-known plasma CVD (Chamical
The 8108 film (silicon oxide film) (23) is deposited to approximately 0% by vapor deposition or photo-CVD method.
゜It is formed to a thickness of 1 μm. Although the insulating film may be made of only the metal oxide layer (22) without forming the film (23), the metal oxide layer (22) may be used as the first insulating layer.
A better insulating film can be formed by forming an insulating film consisting of two layers: and a second insulating layer of Sin and l1l (23). In plasma CVD, the semiconductor substrate (1) is heated to a temperature of about 350°C, but since a metal oxide layer (22) is formed on the upper surface of the S thin layer (3), the process is similar to the thermal oxidation process described above. There is no problem.

Subsequently, as shown in FIG. 3(D), a SiO□ film (23
) on the top surface of the metal layer (24) made of AQ and having a thickness of approximately 2 μm.
is formed by a well-known vacuum evaporation method. metal jlill
Vacuum deposition of (24) is a general method that does not involve cooling the semiconductor substrate (1), but the upper surface of the S thin layer (3) is composed of a metal oxide layer (22) and an Sio2 film (23). Since an insulating film is formed, no problem arises as in the oxidation process described above.

In the MIS structure formed as described above, SUM
Since the insulating film and metal layer can be formed on the top surface of the S thin layer (3) while minimizing the dissociation of S atoms from the S layer (3), the surface stabilization effect of the S thin layer (3) is good. It is possible to obtain good MIs characteristics.

Hi - A handful of summer Various modifications can be made to the above-described embodiments of the invention.

For example, to form the S thin layer (3), Examples 1 and 2
A method using ammonium sulfide solution treatment is preferred. However, the S thin layer (3) may also be formed by a method using other solution treatments such as sodium sulfide.

Also, the surface stabilizing effect of the 8w1 layer (3) is as follows.

- Contains Ga, represented by Ga As, as a lifelong component.
Group II compound semiconductors (GaAs, GaP (gallium phosphide), GaAsP (gallium arsenide phosphide), GaA
11 As (gallium aluminide arsenide), etc., the compound semiconductor region (2) may be made of these compound semiconductors.

Furthermore, cooling of the semiconductor substrate (1) is particularly important at the initial stage of forming the coating layer. This initial stage is the period until the coating layer is formed to a thickness of about 10 layers according to experience. Therefore, the coating layer is 10 people, preferably 50 people.
It is preferable to form the coating layer by cooling the semiconductor substrate (1) so that the overall temperature of the semiconductor substrate (1) is about 150° C. or less, preferably about 1100° C. or less, until the coating layer is formed to a human thickness.

As a result, the effect of preventing the 5J7i molecules from dissociating from the S thin layer becomes significant. After the initial stage, the coating layer can be formed continuously at the same temperature or at a higher temperature.

For the coating layer, various materials can be selected as required.For example, Si is vacuum-deposited using quartz and alumina as a deposition source.
It may be an insulating layer such as n, film or Afi, Ga film. However, since metal layers are more prone to migration (movement of constituent atoms) than insulating layers, they are relatively suitable for low-temperature surfaces. Since it is easier to form a layer with a good film quality, it is easier to set the manufacturing conditions when the coating layer is a metal layer. Note that the metal layer to be converted into an insulating layer must be easily oxidized and converted into an insulator, and AQ and Ta (tantalum)
is suitable.

When creating the metal oxide layer (22) by oxidizing the metal layer (21) as in Example 2, the thickness of the metal layer (21) is reduced by about 300 mm to facilitate oxidation. It is practical to do so. Further, in order to reliably cover the S thin layer (3), it is practical to set the thickness to 10 Å or more. Metal layer (21)
The oxidation method may be appropriately selected from thermal oxidation, plasma oxidation, anodic oxidation, etc. If the metal layer (21) is extremely thin, about 10 layers, natural oxidation or similar light thermal oxidation may be used.

As described above, according to the present invention, a coating layer can be formed on the S thin layer formed on the surface of a compound semiconductor region without substantially impairing the surface stabilizing effect of SUN. . Therefore, the Schottky barrier and ohmic contact, as well as the surface protection structure and MIS structure using an insulator coating, can be formed to have good characteristics, respectively, and contribute to improving the characteristics and manufacturing yield of semiconductor devices using compound semiconductors. .

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of an ultra-high vacuum type vacuum evaporation apparatus, and FIG. 3 is a process diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention. FIG. 2 is a process diagram showing a method for manufacturing a semiconductor device according to an example. (1), Semiconductor substrate, (2), Compound semiconductor region, (3), S thin layer, (4), (21)0. Metal layer (coating layer), (13), Cooler, (22
), Metal oxide layer (first insulating layer) (23), Silicon oxide film (second insulating layer) Patent applicant Sunken Electric Co., Ltd. (and one other person) Agent Yogo Shimizu (Haga 1 person) ＼１、′ Figure 1 2nd cause

Claims (5)

[Claims] (1) After forming a thin layer made of S (sulfur) on the surface of the compound semiconductor region of a semiconductor substrate having a compound semiconductor region containing Ga (gallium) as a main component, attaching the semiconductor substrate to a cooler. A method of manufacturing a semiconductor device, characterized in that a coating layer is formed on the upper surface of the thin layer while the semiconductor substrate is cooled. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the coating layer is formed by vacuum evaporation while the semiconductor element is cooled to −50° C. or lower until the coating layer reaches a thickness of 10 Å. (3) After forming a thin layer of S (sulfur) on the surface of the compound semiconductor region of a semiconductor substrate having a compound semiconductor region containing Ga (gallium) as a main component, the semiconductor substrate is cooled and Forming a covering layer made of metal on the upper surface of the thin layer, oxidizing the covering layer to form a first insulating layer, and then further forming a second insulating layer on the upper surface of the first insulating layer. A method for manufacturing a semiconductor device, characterized by: (4) The method for manufacturing a semiconductor device according to claim 3, wherein the covering layer is formed by vacuum deposition while the semiconductor element is cooled to -50°C or lower until the thickness of the covering layer reaches 10 Å. (5) The layer thickness of the coating layer is 300 Å or less (
3) or the method for manufacturing a semiconductor device according to (4).