JP3079653B2 - Method for synthesizing diamond and zinc blende type compounds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas phase synthesis method of diamond and / or zinc blende type compounds, 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 proceeding at a rapid pace. The utilization of diamond as a semiconductor is one of the main application fields, and expectations for high-temperature diamond and high-speed devices are increasing. Silicon (S
The foundation of the semiconductor industry, such as i) and gallium arsenide (GaAs), is based on high-quality crystal growth techniques, which is also the case for diamond.

Therefore, p-type and n-type semiconductors having high quality and few defects
It is considered to be a very important technique to epitaxially grow a diamond-type diamond film and to produce a flat and clean surface at the atomic level of the grown crystal. Heretofore, for the epitaxial growth of diamond by vapor phase synthesis, i) the (001) plane has been used as a condition for obtaining a flat surface shape [Reference: JP-A No. 1-10
3994, Japanese Patent Application Laid-Open No. 1-246867], ii) When synthesizing by a microwave plasma CVD method in a methane and hydrogen system, the synthesis 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]. Microwave plasma CVD on (001) plane
If the film is formed at a methane concentration of 6% by the method, a flat film can be obtained, but secondary particles grow on the surface due to slight deviation of the conditions, resulting in a rough surface. Met. After a diamond single crystal is formed on a diamond substrate, 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.

[0004] Due to the nature of the diamond structure, the (001) plane of diamond has a surface C at every atomic layer step.
The direction of the bond of the atom is rotated by 90 degrees around <001>. Therefore, as shown in FIG. 4, one of the surface superstructures formed on the clean surface of the (001) plane with one atomic layer step has a 2 × 1 structure and the other has a 1 × 2 structure (FIG. 1). In the case of a step of two atomic layers, the upper and lower layers have the same periodic structure as shown in FIG. 2 (FIG. 2). Generally, the surface has many steps of one atomic layer, and both the 1 × 2 structure and the 2 × 1 structure are formed on the surface. Consider a case where a zinc blende type material is grown on a diamond (001) plane. In a zinc blende compound, when considering an atomic layer perpendicular to <001>, not only the orientation of the bonding hand rotates but also the type of atoms constituting the plane changes. For example, in cBN, a layer composed of B atoms and a layer composed of N atoms are repeated for each layer. When growing cBN on diamond, a B atom is bonded on a C atom, so that CCCCCCCCBBNBBN- NBN ... ← ・ ・ ・ Diamond substrate → ← cBN epitaxial film ・ ・ ・ ・ ・ ・ → If there is a monolayer step on the surface, growth on both sides become that way. That is, as shown in FIG. 5, a portion where an anti-phase boundary (anti-phase domain boundary) such that a cBN crystal having a period of two layers of B and N is shifted by a half period grows on the terrace above the step, It is formed between the parts grown on the terrace below the steps. At such a boundary, the crystal becomes discontinuous. On the other hand, if there are diatomic steps, Like to grow). In this case, as shown in FIG. 3, the step shift corresponds to one cycle of the cBN cycle, so that there is no phase shift as in the case of one atomic layer step. As such, the diatomic layer step does not adversely affect growth. Therefore, when growing cBN on diamond, it is desirable that there be no steps on the surface or that only the steps of diatomic layers be made. Since it is almost impossible to obtain a surface without any steps, it is necessary to control the surface to have only two atomic layer steps. On such a surface, the surface superstructure has only 2 × 1 or only 1 × 2 structure (this is called a single domain). Si is a semiconductor having a diamond structure, and when GaAs, SiC or the like, which is a zinc-blende type semiconductor material, is grown on the (001) plane, a surface without one atomic layer step is necessary. Several conditions have been proposed for obtaining this [for example, Sakamoto et al, Japanese
Journal of Applied Physics Letter vol. 47 (1985)
p.617], and a patent has been filed (for example,
No. 80795).

[0005]

However, with respect to diamond, a diamond substrate or a diamond epitaxial layer manufactured by a conventionally known method is not completely flat at the atomic size level, but is innumerable. The surface contained atomic layer steps. The present invention has been made in view of the above situation, and an object of the present invention is to provide a method for synthesizing a single crystal film of diamond and / or zinc blende type compound having excellent crystallinity on a diamond single crystal substrate. Is to do.

[0006]

According to the present invention, there is provided a synthesis method for epitaxially growing a diamond and / or zinc blende compound on a substrate from a gas phase, wherein the substrate has a plane orientation of <001. > To <
A synthesis method characterized by using a single-crystal diamond substrate shifted within a range of 2 ° to 20 ° in a direction of 110> ± 15 °. Particularly preferred examples of the zinc blende type compound in the present invention include boron nitride, GaAs and SiC.

[0007]

Since diamond is the hardest substance and is difficult to polish, the main crystal planes are (111) and (00).
Although there have been studies on the epitaxial growth of 1), (110), etc., there have been no studies on delicate conditions in which the plane orientation is slightly shifted. The present inventors have conducted detailed experiments for growing diamond and / or heterogeneous materials by vapor phase synthesis on diamond substrates cut and polished in various plane orientations using electron diffraction, electron microscope, tunnel microscope, and the like. Was done. As a result, in homoepitaxial growth in which diamond was grown on diamond, the best surface morphology was obtained when the growth plane orientation was shifted from <001> to <110> by several degrees. This is because microwave plasma CVD, hot filament CV
In each of the D method and the DC plasma CVD method, when a substrate having the above-described plane orientation was used, a surface shape flatter than other sample substrates was obtained. 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 consideration of the lattice constant with diamond.

Although the mechanism by which the method of the present invention improves the surface morphology has not been clearly elucidated, the <110> orientation is a direction corresponding to the (001) surface step, and is shifted by several degrees. As a result, it is considered that the density of the steps increased, and as a result, the crystal growth occurred uniformly over the entire surface. Plane orientation <001
> Is preferably shifted by about several degrees. When the angle is less than 2 °, the effect is almost the same as when the substrate of (001) ± 0.1 ° is used, and there is almost no effect. When the angle exceeds 20 °, the opposite effect was obtained. The <110> direction is most preferable as the direction for shifting, and (001) in 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 make a deviation of about 5 ± 1 ° in the direction of <110> ± 5 °,
Conditions under which a (001) substrate forms a considerably uneven film (for example, microwave plasma C in a methane or hydrogen system)
Even when the methane concentration was set to 1% by the VD method), the morphology was flat.

When a substrate of (001) ± 3 ° is used, the surface after growth has a 2 × 1 structure and a 1 × structure as shown in FIG.
Two superstructures of two structures have been formed (double domain), with one atomic layer step 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 boundary).
On the other hand, FIG. 2 shows a substrate on which good results were obtained by homoepitaxial growth, that is, a case where the plane orientation was shifted by about 5 ± 1 ° from <001> in the direction of <110> ± 5 °. Thus, 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 diamond biatomic step is shown in FIG. That is, the substrate according to the present invention is a zinc-blende type material as shown in FIG.
It was found that the substrate was effective as a substrate for heteroepitaxial growth.

[0010]

【Example】

Example 1 A diamond substrate formed by a high-pressure synthesis method was polished such that the normal direction of the substrate surface was shifted from the <001> direction to the <110> direction by 5 ° as shown in FIG. 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 the growth was found to be a flat surface with a secondary grain growth density of 1 / mm ² or less. When diamond was 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 secondary grains were observed (Comparative Example 1).

Example 2 On a substrate manufactured under the same conditions as in Example 1, a substrate temperature of 9
Diamond was grown for 1 hour at 00 ° C. and a microwave plasma power of 400 W, and SiC was grown thereon for 2 hours. The reflected electron diffraction (RHEED) pattern was observed after diamond growth and after SiC growth. In the RHEED pattern after diamond growth, a double period structure was formed only in the <110> direction, and no long period in the <110> direction was observed. S by RHEED observation
The iC layer was found to be a perfect single crystal. Example 2 for (001) substrate (within ± 1 °) with almost no displacement
The same experiment was performed, and after diamond growth, 2
Twice the period was observed in one direction. It was found that the SiC layer had poor crystallinity and contained a considerable amount of polycrystalline components.

[0012]

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

[Brief description of the drawings]

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

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

FIG. 3 is a schematic diagram of cBN grown on a diatomic 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).

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-103994 (JP, A) JP-A 1-246867 (JP, A) JP-A 2-180795 (JP, A) JP-A-4- 214099 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C30B 1/00-35/00

Claims (2)

(57) [Claims] In a synthesis method for epitaxially growing a diamond and / or zinc blende compound from a gas phase on a substrate, the substrate has a plane orientation of <001> to <1.
A synthesis method characterized by using a single-crystal diamond substrate shifted in a direction of 10> ± 15 ° within a range of 2 ° to 20 °. 2. The method according to claim 1, wherein the zinc blende type compound is boron nitride, G
2. The method according to claim 1, wherein the method is aAs or SiC.