JPH0524989A - Method for synthesizing diamond and sphalerite type compound - Google Patents

Abstract

PURPOSE:To provide a vapor phase synthesis method eptaxially growing diamond and/or sphalerite type compounds having a flat surface shape. CONSTITUTION:In the method for eptaxially growing diamond and/or sphalerite type compounds by vapor phase on a substrate, as the substrate, a single crystal diamond substrate in which its face orientation has been deviated in the range of 2 to 20 deg. in the direction of <001> to <110>+ or -15 deg. is used, by which single crystals excellent in crystalline properties and surface flatness can be synthesized on the substrate. As the sphalerite type compounds, cBN, GaAs and SiC can preferably be given.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vapor phase synthesis method of diamond and / or sphalerite compound, and more particularly to the above synthesis method using a diamond substrate.

[0002]

2. Description of the Related Art In recent years, various kinds of diamond vapor phase synthesis methods have been developed, and the application of diamond films to the industrial field is rapidly progressing. Utilization of diamond as a semiconductor is one of the main fields of application, and expectations for diamond high temperature and high speed devices are increasing. Silicon (S
The basis of the semiconductor industry such as i) and gallium arsenide (GaAs) is high quality crystal growth technology, and this is also applicable to diamond.

Therefore, p-type and n-type having high quality and few defects
It is considered that the epitaxial growth of the diamond-type diamond crystal film and the production of a flat and clean surface at the atomic level of the grown crystal are very important techniques. Up to now, for epitaxial growth of diamond by vapor phase synthesis, i) (001) plane has been used as a condition for obtaining a flat surface shape [Reference: JP-A-1-10].
3994, Japanese Patent Laid-Open No. 1-246867], ii) When synthesizing by a microwave plasma CVD method in a methane or hydrogen system, it should be performed under a high methane concentration condition of about 6% [Reference: H. Shiomi et al, Japanese Journal of A
pplied Physics vol.29 (1990) p.34], etc. have been reported. Microwave plasma CVD on (001) plane
When a methane concentration of 6% is formed by the method, a flat film is certainly obtained, but a slight deviation of the conditions causes secondary particles to grow on the surface, resulting in an uneven surface. Met. After forming a diamond single crystal on the diamond substrate, the cubic boron nitride (c
Heteroepitaxial growth of heterogeneous crystals such as BN) and silicon carbide (SiC) is a technology that has a great significance in expanding the application range of diamond semiconductors.

Due to the nature of the diamond structure, the (001) face of diamond has a C surface at every atomic layer step.
The orientation of the atomic bond is rotated 90 degrees around <001>. Therefore, as shown in FIG. 4, one surface has a 2 × 1 structure and the other surface has a 1 × 2 structure as shown in FIG. 4 (FIG. 1). In the case of the step of two atomic layers, as shown in FIG. 2, the periodic structure is the same both above and below (FIG. 2). Generally, there are many steps of one atomic layer on the surface, and both 1 × 2 structure and 2 × 1 structure are formed on the surface. Consider the case where a zinc blende type material is grown on a diamond (001) surface. In the zinc-blende type compound, when the atomic layer perpendicular to <001> is considered, not only the direction of the bond rotates but also the kind of atoms constituting the plane changes. For example, in cBN, a layer made of B atoms and a layer made of N atoms are repeated for each layer. When cBN is grown on diamond, the B atom is bonded to the C atom, so that C—C—C—C—C—C—C—B—N—B—N—B— N-B-N ... ← ... Diamond substrate → ← cBN epitaxial film ... If there is a monoatomic step on the surface, the growth on both sides of it will be become that way. That is, as shown in FIG. 5, a portion where an antiphase boundary (antiphase domain boundary), which is obtained by shifting a cBN crystal having two layers of B and N as a period by a half period, grows on the terrace above the step, It will be formed between the grown parts on the terrace under the step. At such a boundary, the crystal becomes discontinuous. On the other hand, if there is a diatomic layer step, Grows like). In this case, as shown in FIG. 3, the step shift corresponds to one cycle of the cBN cycle, so that the phase shift does not occur as in the case of one atomic layer step. Therefore, the diatomic step does not adversely affect the growth. Therefore, when growing cBN on diamond, it is desirable that there be no steps on the surface or only diatomic layer steps. Since it is almost impossible to obtain a surface with no steps, it is necessary to control the surface so that there are only two atomic layer steps. On such a surface, the surface superstructure is only 2 × 1 or 1 × 2 structure (this is called a single domain). Si is a semiconductor having a diamond structure, and in the case of growing a zinc blende type semiconductor material such as GaAs or SiC on its (001) plane, a surface without one atomic layer step is required. Several conditions have been proposed for obtaining this [for example, Sakamoto et al, Japanese.
Journal of Applied Physics Letter vol. 47 (1985)
p.617], a patent has also been applied (for example, Japanese Patent Laid-Open No. 2-1
No. 80795, etc.).

[0005]

However, regarding diamond, a diamond substrate or a diamond epitaxial layer produced by a method known so far is not perfectly flat at the atomic size level, and countless single atoms are present. It was a surface containing atomic layer steps. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method capable of synthesizing a single crystal film of diamond and / or a zinc blende type compound having excellent crystallinity on a diamond single crystal substrate. To do.

[0006]

As a means for solving the above problems, the present invention provides a synthetic method of epitaxially growing a diamond and / or a zinc blende type compound on a substrate from a vapor phase, wherein the substrate has a plane orientation of <001. > To <
There is provided a synthetic method characterized by using a single crystal diamond substrate deviated within a range of 2 ° to 20 ° in a direction of 110> ± 15 °. Particularly preferable zinc blende type compounds in the present invention are boron nitride, GaAs or SiC.

[0007]

Since diamond is the hardest substance and it is difficult to polish it, the main crystal faces are (111), (00
Although there have been studies of epitaxial growth for 1) and (110), there have been no studies under delicate conditions in which the plane orientation is slightly shifted. The inventors of the present invention have conducted detailed experiments to try to grow diamond and / or a different substance by a vapor phase synthesis method on a diamond substrate cut and polished in various plane directions by using electron diffraction, an electron microscope, a tunnel microscope and the like. I went. As a result, in homoepitaxial growth in which diamond is grown on diamond, the best surface morphology was obtained when the growth plane orientation was deviated from the <001> orientation to the <110> orientation by several degrees. This is a microwave plasma CVD method, a hot filament CV, regardless of the vapor phase synthesis method.
In both the D method and the DC plasma CVD method, when the substrate having the above-mentioned plane orientation was used, a flatter surface shape was obtained as compared with the other sample substrates. Examples of zinc blende type compounds epitaxially grown on a diamond substrate according to the present invention include cBN, SiC, GaAs, GaP and InA.
Although s, InP and the like can be mentioned, cBN, SiC and GaAs are particularly preferable in view of the lattice constant with diamond.

Although the mechanism by which the surface morphology is improved by the method of the present invention is not clearly understood, the <110> orientation is the direction corresponding to the step of the (001) surface and is shifted by several degrees. It is considered that, as a result, the step density increased, and as a result, crystal growth became uniform over the entire surface. Face orientation is <001
It is preferable that it is deviated by several degrees from>. Below 2 °, there was almost no effect as in the case of using the (001) ± 0.1 ° substrate. If it exceeds 20 °, the effect is opposite. The <110> direction is most preferable as the direction of deviation, and (001) is within the range of <110> ± 15 °.
Better results were obtained. Therefore, it is preferable that the angle is deviated from the <001> direction in the direction of <110> ± 15 ° within the range of 2 to 20 °. In particular, it is most preferable to add a deviation of about 5 ± 1 ° in the direction of <110> ± 5 °,
Conditions such that a considerably uneven film is formed on the (001) substrate (for example, microwave plasma C in methane or hydrogen system).
The morphology was flat even when the methane concentration was set to 1% by the VD method).

When a (001) ± 3 ° substrate was used, the surface after growth had a 2 × 1 structure and a 1 × structure as shown in FIG.
Two superstructures of two structures are formed (double domain), and there is a monolayer of steps on the surface.
FIG. 5 shows a schematic diagram of cBN grown on one atomic layer step of diamond (001). It can be seen that the crystals are discontinuous (anti-phased bandary).
On the other hand, a substrate for which good results are obtained by homoepitaxial growth, that is, when the plane orientation is shifted from <001> by about 5 ± 1 ° in the direction of <110> ± 5 °, the results are shown in FIG. It was confirmed by electron diffraction and a tunnel microscope that the superstructure formed on the surface was only a 2 × 1 structure (single domain). A schematic diagram of cBN grown on this diatomic layer step of diamond is shown in FIG. That is, the substrate according to the present invention is a zinc blende type material.
It was found that this is an effective substrate for heteroepitaxial growth.

[0010]

【Example】

Example 1 As shown in FIG. 1, a diamond substrate prepared by a high-pressure synthesis method was polished so that the substrate surface had a direction deviated by 5 ° from the <001> direction to the <110> direction, and microwave plasma CVD was performed. The epitaxial growth was performed by the method. The synthesis conditions were a pressure of 40 Torr, a substrate temperature of 880 ° C., a microwave power of 400 W, and a growth time of 10 hours. As a result of observation with a Nomarski microscope, the surface after growth was found to be a flat surface with a secondary grain growth density of 1 particle / mm ² or less. When diamond is grown under the same conditions as in Example 1 using a (001) substrate (within ± 2 °) with almost no deviation, 100 to 10,000 / mm
² of secondary grains was observed (Comparative Example 1).

Example 2 On the substrate manufactured under the same conditions as in Example 1, the substrate temperature 9
Diamond was grown for 1 hour at 00 ° C. with microwave plasma power of 400 W, and SiC was grown for 2 hours on it. A backscattered electron diffraction (RHEED) pattern was observed after diamond growth and after SiC growth. In the RHEED pattern after diamond growth, a doubled periodic structure was formed only in the <110> direction, and a long period in the <110> direction was not observed. S by RHEED observation
It was found that the iC layer was a perfect single crystal. Example 2 for (001) substrate (within ± 1 °) with almost no deviation
After performing the same experiment as above, 2
Twice the period was observed in one direction. It was found that the SiC layer had poor crystallinity and contained a large amount of polycrystalline components.

[0012]

According to the present invention, single crystals of single crystal diamond and / or zinc blende type compound having excellent crystallinity and surface smoothness can be synthesized on a diamond single crystal substrate.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a shift of a diamond substrate in Example 1.

FIG. 2 is a schematic view showing a surface having a structure of only 2 × 1.

FIG. 3 is a schematic diagram of cBN grown on a diatomic layer step of diamond (001).

FIG. 4 is a schematic view showing a surface having a 2 × 1, 1 × 2 structure.

FIG. 5 is a schematic diagram of cBN grown on one atomic layer step of diamond (001).

Claims (2)

[Claims] 1. A synthetic method for epitaxially growing diamond and / or sphalerite compound from a vapor phase on a substrate, wherein the substrate has a plane orientation of <001> to <1.
A method for synthesizing, characterized in that a single crystal diamond substrate deviated within a range of 2 ° to 20 ° in a direction of 10> ± 15 ° is used. 2. The zinc blende type compound is boron nitride, G
It is aAs or SiC, The synthetic method of Claim 1 characterized by the above-mentioned.