JPS63179516A - Manufacture of silicon carbide single crystal - Google Patents

Abstract

PURPOSE:To make it possible to suppress the occurrence of defects in laminated layers, by making the crystal growth face of a substrate be not in parallel with a plane (0001) and plane (0001'). CONSTITUTION:The crystal growth face of a substrate is made to be a face, which is neither in parallel with a plane (0001) nor a plane (0001'). For example, the plane (0001), which is the face of a 6H-SiC single-crystal substrate 3, is cut and polished in a slant direction. The face, which is not in parallel with the plane (0001) that is obtained by polishing and the like, is formed and made to be a crystal growth face. A 6H-SiC single-crystal is epitaxially grown on the substrate 3. When Si atoms and C atoms are bonded at a growth interface, strong actions are applied in two orthogonally intersection directions. Thus the arrangement pattern of the atoms in the growth layer 4 is hard to slip, and the occurrence of defects in laminated layers is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a silicon carbide single crystal, which comprises epitaxially growing a hexagonal silicon carbide single crystal on a hexagonal silicon carbide single crystal substrate.

[Conventional technology]

In general, silicon carbide (SiC) has attracted attention as an environmentally resistant semiconductor material due to its physical and chemical properties such as excellent heat resistance, mechanical strength, and resistance to radiation9.
Moreover, 8iC crystal is an indirect transition type 1-N compound, and 8iC crystal has various crystal structures such as cubic and hexagonal for the same chemical composition, and its forbidden band width is 2.89.
~B, 88 eV, which is a wide range, and it is possible to form a pn junction, so it is considered promising as a light-emitting diode material that emits visible light in the entire wavelength range from red to blue. 6H type SiC crystal, which is a type of hexagonal crystal with band width, is used as a material for blue light emitting diodes.

The production of blue light emitting diodes is usually carried out by liquid phase epitaxial growth (LPE) or vapor phase chemical reaction deposition (C0VD).
As a specific example, Journal Op Applied
Physics 50 (12), Disenpa 1979,
8215-8225 (Journal of App
Lie, dPhysics 50(12), De
cember 1979, 8215-8225),
As a specific example of the latter CVD method, Japanese Journal Op Applied Physics 19(7),
Schlei 1980, La58~L856 (JA
PANESE JOURNAL OF APPLIE
D PHYSIc8 19(7).

JULY 1980, L358-L856), and in both cases, the (0001) plane is used as the crystal growth plane of the 6H type 8iC single crystal substrate used for epitaxial growth.

By the way, as mentioned above, SiC crystal has cubic system,
There are various crystal structures belonging to the hexagonal system and the rhombohedral system, and these are called crystal polymorphs, and all have a close-packed structure.
In the case of cubic crystal system, S is on the plane perpendicular to the <111> direction.
If the i atoms are arranged without any gaps and the hexagonal system is <0001
In the case of the <111> direction and the rhombohedral crystal system, Si atoms are arranged without gaps on planes perpendicular to the <111> direction, and these S
A C atom is bonded directly above the i atom to form a constituent unit of SiC.

In this case, a close-packed structure refers to a structure in which spheres of the same size are stacked most densely, and a crystal structure in which the centers of the spheres are the lattice points.For example, as shown in Figure 2, multiple spheres of the same size If we line up the balls without any gaps so that their centers are located at point A in the figure, and if we also line up multiple balls of the same size without gaps on top of them, we can arrange them as shown in the figure. There are two ways to arrange them so that their centers are located at point B and to arrange them so that their centers are located at point C in the figure.If you arrange them so that their centers are located at point B as the second layer, The center of the next 8th layer is located at point C or point A, and if the second layer is arranged so that its center is located at point C, the center of the next 8th layer is located at point B6 or point A. This makes it possible to arrange them in many ways.

In an actual SiC crystal, it is thought that one atomic pair of a Si atom and a C atom corresponds to one sphere in FIG. Therefore, these correspond to the crystal polymorphs mentioned above, and each crystal polymorph of 8iC has a different forbidden band width, and the 8i0 atomic array arrangement of the fundamental period of a typical crystal polymorph and its forbidden band width. are shown in Table 1. In addition, in the display of crystal polymorphism in the table, the numbers '3'', °'15''' and 6'' are the number of layers included in one period, and 'C', H' and R' are the numbers respectively. Cubic, hexagonal, and rhombohedral crystals are represented using English acronyms, and the arrangement pattern is °′A”.

Table 1 1T B 11 , 11 (:” indicates the arrangement pattern in a close-packed structure whose centers are respectively located at points A, B, and 0 in FIG. 2 described above.

Therefore, if the atomic arrangement pattern in a cross section perpendicular to the surface of a 6H type 8iC single crystal substrate is schematically represented, it will be as shown in FIG. 3, and the A-B-C-A-C -B is repeated.

Furthermore, the front surface of the normally obtained 6H-SiC single crystal substrate is the (0001) plane or (0001) plane, and conversely, the back surface is the (0001) plane or (0001) plane,
At this time, if Si atoms are lined up on the surface, it will be a (0001) plane, and if C atoms are lined up, it will be a (0001) plane.
It is possible for Si atoms or C atoms to line up on both the front and back sides due to the crystal structure.The same thing with 6H-8iC single crystals is true for other hexagonal crystal polymorphs such as 8H, 4H, and 2H types. But it applies.

In this way, the surface of the 6H-8iC single crystal substrate is usually (0
001) plane or (0001) plane, 6H-8i
When a 6H-8i0 single crystal is epitaxially grown on a C single-crystal substrate, the (0001) plane or the (0001) plane parallel to this has conventionally been used as the crystal growth plane of the substrate, as described in the above-mentioned Ryorinmon. For example, (
0001) as the crystal growth plane, as shown in Figure 4, a new epitaxial layer grows while receiving interaction with the lower epitaxial layer in the direction of the arrow in the figure, which is parallel to the crystal growth direction. I will do it.

However, Fig. 4 shows 6H-8i0 single crystal substrates (υ and 6H-
A cross section of the interface with the epitaxial growth layer (2) of 8iC single crystal is shown.
is the above-mentioned arrangement pattern, and the shaded area is the growth layer (2
].

At this time, as shown in FIG. 4, even if the surface of the substrate (1) has a very good specularity, when viewed microscopically, there are small protrusions A/ , B/ , c on the order of atoms. / is present, and in the initial growth stage of the epitaxial growth layer (2), that is, in the growth stage of the first layer and the second layer, the projection A'.

Because of n/ and c/, it grows while receiving interaction in the direction perpendicular to the direction of the arrow in the figure.

[Problem that the invention seeks to solve]

However, the 6H-8iO single crystal substrate (1) shown in FIG.
If the epitaxial growth of 6H-8iC single crystal progresses normally on the substrate (
It should be possible to form epitaxial growth H(2) with an arrangement pattern of A-B-C-A-C-B with the same fundamental period as υ, but in reality, for example, A and C patterns are grown on a C pattern layer. Although the layers should grow sequentially, as shown in Figure 4, the 0.A pattern layer grows sequentially on the C pattern layer, resulting in a stacking fault where the pattern of the grown layer (2) is partially reversed. An abnormality called `` occurs and epitaxial growth occurs 6
This causes a decrease in the crystallinity of the H-8iC single crystal, and if a blue light emitting diode is manufactured using a 6H7SiC single crystal with such defects, the yield will decrease and the emission wavelength will become longer and the brightness will decrease. The reason for the occurrence of such defects is that the interaction in the direction perpendicular to the direction of the interaction is weak compared to the strength of the interaction from the underlying Evita Kinyar layer.
It is considered that some slippage occurs in the atomic arrangement pattern in the perpendicular direction. - Therefore, the technical problem of the present invention is to suppress the occurrence of stacking faults and to obtain a 6H-8iC single crystal with good crystallinity.

[Means for solving problems]

This invention was made with the above points in mind,
In a method for manufacturing a silicon carbide single crystal in which a hexagonal high-order silicon single crystal is epitaxially grown on a hexagonal silicon carbide single crystal substrate, the crystal growth plane of the substrate is a (0001) plane, a plane that is not parallel to the (oooT) plane. This is a method for producing a silicon carbide single crystal, which is characterized by the following.

[For production]

Therefore, according to the present invention, the crystal growth plane of the hexagonal formalized silicon single crystal substrate is the (0001) plane, the (0001)
If the plane is not parallel to the plane, the (0001') plane of the substrate, (0
001) The interaction from the lower layer in the direction parallel to the plane becomes stronger than in the past, and the slippage of the atomic arrangement pattern in the epitaxially grown layer in the parallel direction is suppressed, and the occurrence of stacking faults is suppressed.

〔Example〕

Next, the present invention will be explained in detail with reference to FIG. 1 showing an embodiment thereof.

Now, to explain the principle of crystal growth, as shown in Figure 1, for example, a 6H-8iC single crystal substrate (3) is cut obliquely to the (0001) plane, which is the surface, and is obtained by polishing. A plane that is not parallel to the (0001) plane is formed as a crystal growth plane, and a 6H-8i0 single crystal is epitaxially grown on the substrate (3).

At this time, the crystal growth plane of the substrate (3) that is not parallel to the (0001) plane obtained by polishing etc. is considered to be step-like when viewed on the atomic order, as shown in Figure 1. , when the epitaxial growth layer (4) shown with diagonal lines in the figure grows on such a crystal growth surface, the growth layer (
4) grows in a direction perpendicular to the (0001) plane of the substrate (3), and as in the conventional case described above, the growth layer (4) grows in the direction of the solid arrow in the figure parallel to the growth direction. At the same time as it receives strong interaction from the lower layer, it also receives strong interaction in the direction of the broken line arrow in the figure, which is perpendicular to the direction of the solid line arrow, due to the stepped portion of the crystal growth surface of the substrate (3).

In other words, when Si atoms and C atoms bond to the growth interface, they receive strong interactions from the two mutually orthogonal directions described above, which makes it difficult for the atomic arrangement pattern in the growth layer (4) to slip. The fundamental period arrangement pattern of (4) is the same as that of substrate (3).

For example, the (0001
) A surface inclined at 2 degrees to the surface was cut and polished to create a paper cutter.
When a wafer was formed by stacking p and n junction layers of 6H-8iO single crystal as a light-emitting layer using the LPE method using this inclined surface as a crystal growth surface, the appearance rate of blue light in the wafer was an average value. 80% 9, as before (000
1) Blue emission appearance rate 60% when the surface is the crystal growth surface
A significant improvement was seen compared to
By suppressing stacking faults, defects that contribute to the formation of trap levels with deep forbidden band levels and non-emissive centers are reduced, and the appearance of low-energy, long-wavelength emission and non-emissive points other than blue emission is reduced This will be significantly reduced compared to .

Here, as the conditions for forming the wafer described above, a dip method was used, the epitaxial growth temperature was about 1700° C., and nitrogen and aluminum were used as n + pi dopants, respectively.

Note that even if the surface of the substrate (3) is a (0001) plane,
Since the (0001) plane is parallel to the (0001) plane, the same effect as in the above example can be obtained, and 8
I(,4H.

Similar effects can be obtained by using a hexagonal 8i0 single crystal substrate such as 2H.

〔Effect of the invention〕

As described above, according to the method for manufacturing a silicon carbide single crystal of the present invention, by making the crystal growth plane of the hexagonal silicon carbide single crystal substrate a (0001) plane, a plane that is not parallel to the (0001) plane, The interaction from the lower layer in the direction parallel to the (0001) plane of the substrate and the (0001) plane, which extends to the epitaxial growth layer that grows on the substrate, can be strengthened compared to conventional methods.
It is possible to suppress the slip in the parallel direction of the atomic arrangement pattern in the epitaxial growth layer, and it is possible to suppress the occurrence of stacking faults, and it is possible to obtain a hexagonal silicon carbide single crystal with good crystallinity. When silicon carbide single crystals such as these are used to manufacture blue light-emitting diodes, it is possible to improve the yield compared to conventional methods, and to produce high-quality blue light that suppresses deterioration of characteristics such as longer emission wavelengths and lower brightness. It becomes possible to obtain a light emitting diode.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the principle of one embodiment of the method for producing a silicon carbide single crystal of the present invention, and FIG. 2 is an explanatory diagram of the close-packed structure of the crystal.
Figure 3 is an explanatory diagram of the atomic arrangement pattern in the cross section of a general hexagonal silicon carbide single crystal substrate, and Figure 4 is the growth interface when a hexagonal silicon carbide single crystal is epitaxially grown on the substrate shown in Figure 3. FIG. 3 is an explanatory diagram of an atomic arrangement pattern in a nearby cross section. (3)...substrate, (4)...epitaxial growth layer.

Claims (1)

[Claims] (1) In a method for manufacturing a silicon carbide single crystal in which a hexagonal silicon carbide single crystal is epitaxially grown on a hexagonal silicon carbide single crystal substrate, the crystal growth plane of the substrate is a (0001) plane and a (000@1) plane.
A method for producing a silicon carbide single crystal, characterized in that the plane is not parallel to the @) plane.