JPH0249422A - Manufacture of silicon carbide semiconductor device - Google Patents

Abstract

PURPOSE:To enable the title silicon carbide semiconductor device to be electrically activated sufficiently even if the device is implanted with group III element ion at around room temperature by a method wherein a silicon carbide semiconductor layer is implanted with silicon ion and group III element ion while a process to form a P type conductive layer is included. CONSTITUTION:A non-doped SiC single crystal layer 2 is deposited on an Si single crystal substrate 1. An SiO2 film 3 is formed on the whole surface of the single crystal layer 2 and then an opening is made in specified region on the SiO2 film 3. Next, an Si ion implanted layer 4 is formed by implanting Si(<28>Si<+>) ion in an opening part in the single crystal layer 2. Successively, a mixed ion implanted layer 5 with Si ion and B ion is formed by implanting B(<11>B<+>) ion in the implanted layer 4. Then, the mixed ion implanted layer 5 is activated to form a p type conductive layer 5' by annealing process in Ar atmosphere. Finally, Al electrodes 6 and 7 are formed by making openings in the specified regions in the film 3 to evaporate aluminum.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a silicon carbide semiconductor device, particularly a silicon carbide semiconductor device having a p-type conductive layer.

(Prior art) In addition to silicon (Si), gallium arsenide (GaAs)
Semiconductor devices (e.g., diodes, transistors, integrated circuits, large-scale integrated circuits, 2 light emitting diodes, etc.) using compound semiconductors such as gallium phosphide (GaP) and gallium phosphide (GaP).

BACKGROUND ART Semiconductor lasers and charge-coupled devices have been widely used in various fields of electronics.

Silicon carbide (SiC) has a wide forbidden band width (2.2~3.3e
V), and has the excellent characteristics of being extremely stable thermally, chemically, and mechanically, and resistant to radiation damage. Semiconductor devices using conventional semiconductor materials such as silicon are difficult to use, especially under harsh conditions such as high temperatures, high power drives, and radiation exposure. Therefore, semiconductor devices using silicon carbide are expected to be applied in a wide range of fields as semiconductor devices that can be used even under such severe conditions.

However, no crystal growth technology has been established that can stably supply silicon carbide single crystals with a large area and high quality on an industrial scale in consideration of productivity.Therefore, silicon carbide is Although semiconductor materials have many advantages and possibilities, their practical application has been hindered.

Conventionally, on a laboratory scale, silicon carbide single crystals have been grown using, for example, the sublimation recrystallization method (Rayleigh method).

Using the silicon carbide single crystal obtained by this method as a substrate.

By epitaxially growing a silicon carbide single crystal layer thereon using vapor phase growth (CVD) or liquid phase epitaxial growth (LP!i), a silicon carbide single crystal of a size that is suitable for prototyping semiconductor devices is obtained. There is. However, with these methods, the area of the obtained single crystal is small, and it is difficult to control its size and shape with high precision. Furthermore, it is not easy to control the crystal polymorphism and impurity concentration of silicon carbide.

In order to solve these problems, the present inventors proposed a method of vapor phase growth of a high-quality silicon carbide single crystal with a large area on an inexpensive and easily available silicon single crystal substrate (particularly (No. 59-203799).

In this method, if an impurity is added during vapor phase growth of silicon carbide, it is possible to control the impurity concentration and conductivity type in the obtained silicon carbide single crystal. However, since the temperature for vapor phase growth is high, the electrical characteristics of a semiconductor device provided with, for example, a pn junction are not very good. Therefore, the above method is not suitable for forming a silicon carbide semiconductor layer doped with impurities.

BACKGROUND ART Impurity thermal diffusion or ion implantation is widely used as an indispensable process technique for manufacturing semiconductor devices using silicon, particularly semiconductor devices with a planar structure.

(Problem to be Solved by the Invention) However, the impurity diffusion constant in silicon carbide is small and a diffusion temperature of 1,600°C or higher is required, so the impurity thermal diffusion method is not suitable as a process technology for silicon carbide semiconductors. do not have.

Regarding the ion implantation method, group V element ions (for example, nitrogen (N) ions and phosphorus (P) ions) are implanted, and silicon carbide into which these ions are implanted becomes electrically active by thermal annealing. become

However, when group Ⅰ element ions are implanted into silicon carbide, the silicon carbide is not sufficiently electrically activated even though the implanted impurity ions are distributed in the silicon carbide as theoretically expected. do not have.

In fact, at a substrate temperature of 823K, aluminum (AI)
An example of ion implantation into silicon carbide (J, A, Edmond
et al.

J. Appl. Phys. 63.922 (1988))
has only been reported by implanting group ■ element ions at around room temperature.

There are no cases where electrical activation has been observed.

The present invention is intended to solve the above-mentioned conventional problems, and its purpose is to achieve sufficient electrical activation even when group (I) element ions are implanted near room temperature. An object of the present invention is to provide a method for manufacturing a silicon carbide semiconductor device having a p-type conductive layer.

(Means for Solving the Problems) The present invention provides a method for manufacturing a silicon carbide semiconductor device having a p-type conduction layer, which comprises adding silicon ions and
forming a p-type conductive layer by implanting group element ions, thereby achieving the above object.

Even if only group Ⅰ element ions are implanted into a silicon carbide semiconductor, it will not be activated. On the other hand, in silicon semiconductors, implanted group Ⅰ element ions are easily activated. Therefore, in the manufacturing method of the present invention.

Silicon ions and group Ⅰ element ions are implanted into the silicon carbide semiconductor layer, and the group Ⅰ element ions are activated in the presence of excess silicon ions. As a result, group (I) element ions in the silicon carbide semiconductor layer are easily activated.

When performing ion implantation, do you first implant silicon ions and then implant group (I) element ions?

Alternatively, silicon ions and Group I element ions can be implanted simultaneously.

Examples of group II element ions to be implanted include boron (B) ions, aluminum (AI) ions, gallium (
Examples include Ga) ions.

(Example) The present invention will be described below with reference to examples.

In this example, a case will be explained in which boron ions are used as the group Ⅰ element ions.

First, as shown in FIG. 1 (° C.), a non-doped SiC single crystal layer 2 was grown on a Si single crystal substrate 1 by a vapor phase epitaxy (CVD) method. Then, after forming an SiO2 film 3 of approximately 1000 m thick over the entire surface of the non-doped SiC single crystal layer 2, as shown in FIG.
An opening was made in a predetermined area by etching.

Next, using an ion implantation device, St (".St") ions are implanted into the opening portion of the non-doped SiC single crystal layer 2, as shown in FIG.

A Si ion implantation layer 4 was formed. As for the injection conditions.

By subsequently implanting B ("B") ions into the Si ion implantation layer 4, the acceleration voltage was 180 keV and the implantation amount of Si ions was 5XIO14C1-".

As shown in FIG. 1(e), a mixed ion implantation layer 5 containing Si ions and B ions was formed. The implantation conditions were that the acceleration voltage was 70 keV and the amount of B ions implanted was IXl01SC1-''.

And 30 at 1.100°C under Ar atmosphere.
The mixed ion implantation layer 5 was activated by performing an annealing treatment for 1 minute. When examined using the thermal probe method and the Hall measurement method, it was found that a p-type conductive layer of 5° (Fig. 1(a)) was formed.

Finally, electrodes 6 and 7 were formed by opening a predetermined region of SiOx film 3 and depositing aluminum to obtain a silicon carbide semiconductor device as shown in FIG. 1(a). Current of the silicon carbide semiconductor device thus obtained -
When the voltage characteristics were measured, as shown by the solid line in FIG. 2, good rectification characteristics were shown.

For comparison, a silicon carbide semiconductor device was manufactured in the same manner except that only B ions were implanted without implanting Si ions. Although such a semiconductor device had a high resistance as indicated by the dotted line in FIG. 2, it did not exhibit rectifying characteristics.

(Effects of the Invention) According to the manufacturing method of the present invention, it is possible to ion-implant group III element ions, which are p-type impurities, into silicon carbide, and a silicon carbide semiconductor device having a p-type conduction layer can be manufactured. can get. The manufacturing method is:

Since ordinary ion implantation technology is used, semiconductor devices such as transistors and integrated circuits using silicon carbide semiconductors can be produced on an industrial scale.

Figure 1(a) is a cross-sectional view of a silicon carbide semiconductor device manufactured by a manufacturing method that is an embodiment of the present invention.
(8) is a cross-sectional view of the silicon carbide semiconductor device in the middle of manufacturing, and FIG. 2 is a current-voltage characteristic of the silicon carbide semiconductor device (
FIG. 4 is a diagram showing current-voltage characteristics (dotted line) of a silicon carbide semiconductor device as a comparative example.

DESCRIPTION OF SYMBOLS 1... St single crystal substrate, 2... Non-doped SiC single crystal layer, 3... 5ift film, 4... Si ion implantation layer, 5... Mixed ion implantation layer, 5'...p Type conductive layer, 6, 7... Alt rod.

that's all Figure 1

Claims (1)

[Claims] 1. A method for manufacturing a silicon carbide semiconductor device having a p-type conductive layer, the p-type conductive layer being formed by implanting silicon ions and group III element ions into the silicon carbide semiconductor layer. A method for manufacturing a silicon carbide semiconductor device, comprising the steps of: