JPH04300298A - Method for liquid-phase epitaxial growth of silicon carbide single crystal - Google Patents

Abstract

PURPOSE:To provide a method for liquid-phase epitaxial growth of a silicon carbide single crystal capable of readily and accurately controlling the concentration of a silicon carbide single crystal carrier to be produced. CONSTITUTION:The subject method is a method for liquid-phase epitaxial growth of a silicon carbide single crystal by dipping a silicon carbide single crystal substrate in a silicon melt and epitaxially growing the silicon carbide single crystal on the aforementioned silicon carbide single crystal substrate. In the aforementioned method, a chip composed of a silicon substrate 1 and a silicon nitride layer 2, formed thereon and having a uniform thickness is used as a doping material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for liquid phase epitaxial growth of silicon carbide single crystals on a silicon carbide single crystal substrate.

0002

2. Description of the Related Art Silicon carbide single crystals are grown by a dip method, which is a type of liquid phase epitaxial growth. That is, as shown in FIG. 4, a crucible 2 made of graphite
1 is filled with silicon, and in an inert gas atmosphere,
The crucible 21 is heated to melt silicon. Then, silicon carbide single crystal substrate 24 fixed to the tip of holder 23 is immersed in silicon melt 22 for a certain period of time, thereby growing a silicon carbide single crystal on substrate 24 .

At this time, the carrier concentration of silicon carbide is controlled by adding a small amount of aluminum or nitrogen as impurities into the crucible 21.

0004

[Problems to be Solved by the Invention] In the above prior art, when growing an n-type silicon carbide single crystal layer, crucible 2
It is common practice to add a small amount of silicon nitride (Si3 N4) to the silicon nitride along with silicon.

However, the weight of silicon nitride to be added is about 1/10,000 to 1/1,000,000 of the weight of silicon. Therefore, it is very difficult to weigh silicon nitride. This causes difficulty in controlling the carrier concentration of the n-type silicon carbide single crystal layer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for liquid phase epitaxial growth of a silicon carbide single crystal in which the carrier concentration of the silicon carbide single crystal to be manufactured can be easily and accurately controlled.

[0007]

[Means for Solving the Problems] The present invention provides a silicon carbide single crystal that is epitaxially grown on the silicon carbide single crystal substrate by immersing the silicon carbide single crystal substrate in a silicon melt. A liquid phase epitaxial growth method is characterized in that a chip consisting of a silicon substrate and a silicon nitride layer of uniform thickness formed thereon is used as a doping material.

[0008]

According to the present invention, since the weight of silicon nitride can be accurately evaluated based on the thickness and size of the silicon nitride layer, the carrier concentration of the silicon carbide single crystal layer to be manufactured can be easily controlled.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 3.

FIG. 1 shows a doping material 10 used in liquid layer epitaxial growth of a silicon carbide single crystal.

In FIG. 1, 1 is a silicon substrate, and 2 is a silicon nitride layer deposited on the silicon substrate 1. In FIG. As a method for depositing silicon nitride 2 on silicon substrate 1, CVD method is generally used. This method uses monosilane (SiH4) and ammonia (NH3) as raw material gases.
) and keeping the temperature of the silicon substrate 1 at approximately 900°C, silicon nitride (
A Si3N4) layer 2 can be deposited. By this method, a silicon nitride layer 2 is formed on a silicon substrate 1 with a thickness of about 5,000 yen.
A thickness of about Å (=0.5 μm) is deposited.

Thereafter, the thickness of the silicon nitride layer 2 is accurately measured using an ellipsometer or a SEM (scanning electron microscope).

[0013] Here, it is known that the density of silicon nitride (Si3 N4) is 3.44 g/cm3, so if, for example, 100 μg of silicon nitride is to be added, the volume of silicon nitride is 2.9×10-5cm3
becomes. Therefore, when the thickness of the silicon nitride layer 2 is 5000 Å, the area corresponding to the volume of 2.9×10 −5 cm 3 is 0.581 cm 2 . That is, 0.581cm
All you have to do is cut out the doping material by the size of 2.

[0014] As a method of cutting out the doping material into a predetermined area, a dicing saw can be used to cut out the doping material into a square shape. The area of the top surface is 0.581
When cutting out a cm2 doping material, the length of one side is 7.62 mm.

FIG. 4 shows the chips cut out in this way.
By adding silicon together with the crucible 21 shown in
Nitrogen will be added as an impurity.

As shown in FIG. 2, a doping material consisting of a silicon nitride layer 2 deposited on a silicon substrate 1 is cut into square chips 11 each having a predetermined side length of 1 mm, for example, by dicing. By adjusting the number of chips 11 to be added, the amount of silicon nitride added can be controlled.

FIG. 3 shows the relationship between the carrier concentration of a silicon carbide single crystal grown using this method and the area of silicon nitride layer 2 in added doping material 10. This figure shows that the carrier concentration is proportional to the area of silicon nitride layer 2. Therefore, if the thickness of the silicon nitride layer 2 is kept constant, the carrier concentration can be controlled simply by adjusting the cutout area of the doping material 10.

[0018]

According to the present invention, the carrier concentration of a silicon carbide single crystal can be easily and accurately controlled, and its reproducibility is also improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a doping material.

FIG. 2 is a plan view showing chips when the doping material is cut out in advance into a plurality of chips of the same size.

FIG. 3 is a graph showing the carrier concentration of a grown silicon carbide single crystal with respect to the area of an added doping material.

FIG. 4 is a schematic configuration diagram showing a liquid phase epitaxial apparatus for producing a silicon carbide single crystal.

[Explanation of numbers]

1 Silicon substrate 2 Silicon nitride layer 10 Doping material 11 Chip

Claims (1)

[Claims] 1. A method for liquid phase epitaxial growth of a silicon carbide single crystal, in which a silicon carbide single crystal substrate is immersed in a silicon melt and a silicon carbide single crystal is epitaxially grown on the silicon carbide single crystal substrate. A method for liquid phase epitaxial growth of a silicon carbide single crystal, characterized in that a chip consisting of a silicon carbide single crystal and a silicon nitride layer of uniform thickness formed thereon is used as a doping material.