JPH04348086A - Liquid phase epitaxy - Google Patents

Abstract

PURPOSE:To provide a liquid phase epitaxial growth method which can easily epitaxially grow single crystals different in kind. CONSTITUTION:Fused liquid 3 for growing first conductivity type, inside a graphite crucible 1, and fused liquid 4 for growing second conductivity type, outside it, are filled. A substrate 6 is dipped in this inner fused liquid 3 so as to epitaxially grow first conductivity type of SiC single crystals on the substrate 6, and then this fused liquid 3 is made to overflow to mix the inner fused liquid 3 with the outer fused liquid 4, and by the compensating effect, the conductivity type is changed to epitaxially grow second conductivity type SiC single crystals on the substrate 6.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid phase epitaxial growth method, and more particularly to a method suitable for producing silicon carbide (hereinafter referred to as SiC) single crystal.

0002

2. Description of the Related Art Silicon carbide (SiC) is attracting attention as an environment-resistant semiconductor material due to its physical and scientific properties such as excellent heat resistance, mechanical strength, and resistance to radiation. In particular, 6H (hexagonal) type SiC crystal has a forbidden band width of about 3 eV at room temperature and is used as a material for blue light emitting diodes.

[0003] A method for growing SiC single crystals on a substrate is described in Electronic Technology, Vol. 26, No. 14, p. 128~P. 1
There is a dip method, which is a type of liquid phase epitaxial growth method, as described in the article "SiC blue light emitting diode" published in No. 29.

This dipping method will be explained with reference to FIG. Silicon (Si) 60 charged in a crucible 50 made of graphite is heated and melted by a high-frequency heating coil disposed outside. The SiC substrate 15 is fitted into the tip of the substrate holder 30 at its tip. The temperature of the silicon melt 60 is maintained at 1600° C. to 1800° C., the substrate holder 30 is lowered into the silicon melt 60, the SiC substrate 15 is immersed therein, and the temperature is maintained for a certain period of time.

Carbon (C) is eluted from the inner wall of the graphite crucible 50 into the silicon melt 60, forming silicon carbide (SiC).
), and a SiC single crystal is grown on the SiC substrate 15 by liquid phase epitaxial growth.

At this time, if a small amount of silicon nitride (Si3N4) is added to the silicon melt 60, nitrogen (N)
acts as a donor in SiC, so an n-type SiC single crystal grows. Similarly, if a small amount of aluminum (Al) is added to the silicon melt 60, aluminum (A
l) acts as an acceptor in SiC, so p-type S
An iC single crystal grows.

Therefore, as shown in FIG.
An n-type SiC single crystal 41 can be grown thereon. Next, by replacing the crucible and growing a p-type SiC single crystal, a p-n junction SiC blue light emitting diode (n-n-p structure) can be manufactured.

[0008]

The above-mentioned liquid phase epitaxial growth method is suitable for obtaining high quality SiC single crystals because the temperature distribution within the crucible can be easily controlled. However, when producing single crystals of different conductivity types (p-type, n-type) or single crystals of the same conductivity type but with different carrier concentrations, two or more types of crucibles (silicon melts) are required.

[0009] Therefore, if only one crucible can be accommodated in the reaction tube, the crucible must be replaced, which makes the process very complicated and time consuming. Furthermore, when a plurality of crucibles are prepared in the reaction tube, it is difficult to control the temperature distribution within each crucible. The present invention was made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a liquid phase epitaxial growth method that can easily epitaxially grow different types of single crystals.

0010

[Means for Solving the Problems] A liquid phase epitaxial growth method according to a first aspect of the present invention includes preparing a graphite crucible whose interior is divided into an outside and an inside, and a first conductive layer inside the graphite crucible. A melt for growing a mold and a melt for growing a second conductivity type are provided on the outside, and a silicon carbide single crystal substrate is immersed in the melt on the inside to form a carbonized silicon carbide of the first conductivity type. After a silicon single crystal is epitaxially grown on a substrate, this melt is allowed to overflow, the inner melt and the outer melt are mixed, and the conductivity type is changed by the compensation effect to form a silicon carbide single crystal of the second conductivity type. It is characterized by epitaxial growth.

A liquid phase epitaxial growth method according to a second aspect of the present invention is a liquid phase epitaxial growth method in which a substrate is immersed in a raw material melt in a graphite crucible to epitaxially grow a single crystal on the substrate. The method is characterized in that a plurality of partition walls are provided inside the substrate, and by sequentially removing the partition plates, the melt is moved and various types of different single crystals are sequentially formed on the substrate.

0012

[Operation] According to the first invention, by overflowing the SiC melt after growing the SiC single crystal of the first conductivity type, the SiC melt becomes suitable for growing the second conductivity type due to the compensation effect. It becomes a melted liquid. Therefore, SiC of the second conductivity type can be melted without lowering the temperature of the crucible and without replacing the contents.
Since single crystals can be formed continuously, the process can be significantly shortened.

According to the second invention, by sequentially removing the partition walls, various types of different single crystals can be obtained in one crucible. Also, since there is only one crucible,
Temperature distribution can be easily controlled.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to drawings showing embodiments thereof.

First, according to FIGS. 1 and 2, the first
An embodiment of the invention will be described. FIG. 1 is a sectional stylized view of an apparatus for carrying out the first method of the present invention.

In FIG. 1, 1 is a graphite crucible, and this crucible 1 is divided by a central wall 2 into an inner melt chamber 3a and an outer melt chamber 4a. This inner melt chamber 3
In the outer melt chamber 4a, there is an n-type silicon melt 3 that grows n-type SiC, and in the outer melt chamber 4a, there is an inner melt 3.
A p-type silicon melt 4 that grows p-type SiC when mixed with the silicon melt 4 is filled. 5 is a board support rod;
A SiC single crystal substrate 6 is supported at its tip. The SiC single crystal substrate 6 supported by the substrate support rod 5 is immersed in the melt in the crucible 1.

Next, the procedure for growing a SiC single crystal on the substrate 6 using this apparatus shown in FIG. 1 will be explained with reference to FIGS. 1 and 2.

First, with the crucible 3 heated to the crystal growth temperature using a high frequency coil (not shown) or the like, the n-type melt 3 filled in the inner melt chamber 3a is heated to the substrate support rod 5 as shown in FIG. The SiC single crystal substrate 6 supported by the substrate is immersed. Since the melt at this time is an n-type melt, an n-type SiC single crystal grows on the substrate 6.

Next, as shown in FIG. 2, Si is placed in the crucible 1.
A C block or the like is inserted to cause the p-type silicon melt 4 to overflow. As described above, the p-type silicon melt 4 mixes with the n-type silicon melt 3 and the Si block, and becomes the p-type silicon melt 4 that causes p-type growth as a whole due to the compensation effect.

As a result, the entire crucible 1 becomes a p-type silicon melt 4, and the SiC single crystal substrate 6 on which the n-type SiC single crystal is grown, supported by the substrate support rod 5, is immersed again into the melt 4. By doing so, a p-type SiC single crystal grows.

[0021] Thus, according to the first invention, S
An n-type SiC layer and a p-type SiC layer can be grown substantially continuously on an iC single crystal substrate without replacing the crucible, and mass productivity of SiC blue light emitting diodes and the like is greatly improved.

Next, a second aspect of the present invention will be explained with reference to FIGS. 3 and 4. FIG. 3 is a schematic cross-sectional view showing an embodiment of the second method of the present invention in the order of steps.

FIG. 3 shows a vertical partition plate system. As this example, a method of creating three types of melts using two partition plates 11 and 12 will be shown. 2 if necessary
It is also possible to have more than one partition plate.

In FIG. 3, 10 is a graphite crucible;
0 is a Si melt, and 11 and 12 are partition plates made of graphite. 1
6 and 17 are aluminum melts for p-type inversion. 3
0 is a substrate holder, and a SiC single crystal 15 is sandwiched in the tip of this substrate holder.

Next, the procedure of the second invention will be explained with reference to FIG.

First, as shown in FIG. 3(a), a region 20a surrounded by the partition plates 11 and 12 is filled with Si melt 20 and held at the growth temperature, after which the substrate holder 30 is lowered. , the SiC single crystal substrate 15 is immersed. A small amount of silicon nitride (Si3N4) is added to this Si melt 20, and an n-type SiC layer is formed on the n-type substrate 15. At this time, a small amount of aluminum (Al) is also added and used as a luminescent center.

Next, as shown in FIG. 3(b), the n-type substrate 1
After forming an n-type light emitting layer on the substrate 5, the substrate holder 30 is once raised. Then, the partition plate 11 is removed. As a result, the melt spreads as shown in the figure, and the aluminum melt 17
is added to the Si melt 20 to turn it into a p-type melt. Lower the substrate holder 30 again and place the Si single crystal substrate 1
5, a p-type layer is formed on the previously formed n-type light emitting layer.

Next, as shown in FIG. 3(c), when the substrate holder 30 is raised again and the partition plate 12 is removed, the melt spreads further and the aluminum melt 16 is added to the Si melt 20, resulting in p+ type Invert to melt.

At this point, the Si single crystal substrate 15 is immersed, and a p+ type layer is formed on the previously formed p type layer.

In this way, as shown in FIG.
are sequentially formed to produce a SiC blue light emitting diode. Here, the last p+ type layer is formed to improve ohmic properties with the ohmic electrode.

FIG. 4 is a schematic cross-sectional view showing a different embodiment of the second invention. In contrast to the embodiment shown in FIG. 3, which uses a vertical partition plate system, FIG. 4 shows a configuration using a horizontal partition plate system.

As shown in FIG. 4, in the horizontal partition plate system, horizontal partition plates 26 and 27 are provided on the crucible 25. The area partitioned by the upper partition plate 26 is filled with Si melt 20, and the aluminum melt 16 is placed on the second partition plate 27, and the aluminum melt 17 is placed at the bottom of the crucible 25. Then, by simply removing the partition plates 26 in order and dropping the Si melt 2 downward, different types of SiC single crystals are sequentially grown and formed on the substrate 15, similar to what was explained with reference to FIG.

The embodiment described above is just an example, and n
It is possible to use not only the -n-p-p+ structure but also the n-n--n+-p structure, and if necessary, it is also possible to manufacture a light emitting diode with a multilayer structure.

[0034]

Effects of the Invention As explained above, according to the liquid phase epitaxial growth method of the present invention, epitaxial growth layers can be sequentially formed without replacing a single crucible, which greatly reduces time and costs. It is also effective for Furthermore, in the conventional method, the pn junction interface was always exposed to the atmosphere, but in the present invention, growth can be performed continuously, so that a good pn junction interface can be obtained.

Furthermore, a multilayer structure of two or more layers can be easily formed.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an apparatus for carrying out the first method of the invention.

FIG. 2 is a schematic cross-sectional view showing the state of crystal growth of the second conductivity type in the first invention method.

FIG. 3 is a schematic cross-sectional view showing an embodiment of the second invention.

FIG. 4 is a schematic cross-sectional view showing another embodiment of the second invention.

FIG. 5 is a cross-sectional view of a liquid phase epitaxial layer formed according to the second invention.

FIG. 6 is a cross-sectional view of a liquid phase epitaxial layer formed by a conventional method.

FIG. 7 is a cross-sectional view showing a conventional liquid phase epitaxial growth method.

[Explanation of symbols]

1 Crucible 2 Central wall 3 Silicon melt 4 Silicon melt 5 Board support rod 6 SiC single crystal substrate 10 Crucible 11 Partition plate 12 Partition plate 15 SiC single crystal substrate 16 Aluminum melt 17 Aluminum melt 20 Silicon melt 25 Crucible 26 Partition plate 27 Partition plate 30　Substrate holder

Claims (2)

[Claims] Claim 1: A graphite crucible having a structure in which the inside is divided into an outside and an inside is prepared, and a melt for growing a first conductivity type is placed inside the graphite crucible, and a melt for growing a second conductivity type is placed outside the crucible. A silicon carbide single crystal substrate is immersed in the inner melt to epitaxially grow a silicon carbide single crystal of the first conductivity type on the substrate, and then the melt is allowed to overflow. A liquid phase epitaxial growth method characterized by mixing an inner melt and an outer melt, changing the conductivity type by a compensation effect, and epitaxially growing a silicon carbide single crystal of a second conductivity type. 2. A liquid phase epitaxial growth method in which a substrate is immersed in a raw material melt in a graphite crucible to epitaxially grow a single crystal on the substrate, the method comprising: providing a plurality of partition walls in the graphite crucible; A liquid phase epitaxial growth method characterized by sequentially removing various types of single crystals on a substrate by moving the melt and sequentially forming different types of single crystals on a substrate.