JPH11106290A - Formation of single crystal diamond film and substrate for vapor-phase synthesis of single crystal diamond film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for forming a single crystal diamond film capable of avoiding reduction in local crystallizability and preventing the occurrence of a twin crystal and to obtain a substrate for the vapor-phase synthesis of the single crystal diamond film. SOLUTION: A single crystal diamond film is synthesized in a vapor phase by using a platinum single crystal substrate having a surface inclined by 1 deg. to 3 deg. from a crystal plane (111). A substrate obtained by coating a silicon base having a surface inclined by 1 deg. to 3 deg. from a crystal plane (111) with a platinum single crystal film, a substrate obtained coating a sapphire substrate having a surface inclined by 1 deg. to 3 deg. from a crystal plane (0001) with a platinum single crystal film or a substrate obtained by coating a quartz base having a surface inclined by 1 deg. to 3 deg. from a crystal plane (0001) with a platinum single crystal film can be used as the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to electronic devices such as transistors, diodes and various sensors, heat sinks, and the like.
Surface acoustic wave device, X-ray window, optical-related material, wear-resistant material, method for forming single-crystal diamond film used for decorative material and its coating, and single-crystal diamond film used for its vapor phase synthesis Regarding the substrate.

[0002]

2. Description of the Related Art Diamond has excellent heat resistance, a large band gap (5.5 eV), and is usually an insulator, but can be made into a semiconductor by doping with impurities. In addition, diamond has excellent electrical characteristics such as a high dielectric breakdown voltage and a high saturation drift velocity, and a low dielectric constant. Due to these characteristics, diamond is expected as an electronic device / sensor material for high temperature, high frequency, and high electric field. In addition, diamond is applied to light sensors and light-emitting elements that support the short wavelength region such as ultraviolet light utilizing the large band gap, and is applied to the heat dissipation substrate material utilizing the large thermal conductivity and small specific heat. Applications to surface acoustic wave devices making use of the property of being the hardest among materials, applications to X-ray windows and optical materials utilizing high light transmittance and refractive index, and the like have been advanced.

[0003] In these various applications, it is necessary to synthesize a high-quality single crystal with reduced crystal structural defects in order to maximize the properties of diamond.
For practical use, a low-cost, large-area single-crystal diamond film is required.

Accordingly, the present inventor has already proposed a method of synthesizing a single-crystal diamond film in a large area at low cost in a gas phase (Japanese Patent Application Laid-Open No. Hei 8-151296). This method is based on (11) of platinum alone or an alloy containing 50% or more of platinum.
1) A method of forming a single crystal diamond film by vapor phase synthesis using the (001) crystal plane as a substrate. Diamond synthesized by this method has an excellent effect that fusion between crystals proceeds spontaneously on the surface and a smooth surface can be obtained.

[0005]

However, this method has the following problems. That is, in the synthesized single crystal diamond film, the crystallinity is lowered at the fusion portion between the (111) crystal planes. In the above method,
There is also a disadvantage that twinning, which is a type of crystal defect, occurs.

The present invention has been made in view of the above problems, and a method and a method for forming a single crystal diamond film capable of preventing a local decrease in crystallinity and preventing twinning from occurring. An object of the present invention is to provide a substrate for vapor-phase synthesis of a crystalline diamond film.

[0007]

According to the present invention, there is provided a method for forming a single crystal diamond film, the method comprising:
It is characterized in that a single-crystal diamond film is vapor-phase synthesized using a platinum single-crystal substrate having a surface inclined at 3 °.

In this method of forming a single crystal diamond film, a substrate in which a platinum single crystal film is coated on a silicon substrate having a surface inclined by 1 ° to 3 ° from the (111) crystal plane instead of the platinum single crystal substrate is used. May be used, (00
01) A substrate in which a platinum single crystal film is coated on a sapphire substrate having a surface inclined by 1 ° to 3 ° from the crystal plane may be used, and has a surface inclined by 1 ° to 3 ° from the (0001) crystal plane. A substrate in which a quartz substrate is coated with a platinum single crystal film may be used.

Further, the substrate for vapor phase synthesis of a single crystal diamond film according to the present invention is characterized in that it is a platinum single crystal substrate having a surface inclined by 1 ° to 3 ° from the (111) crystal plane.

Further, another substrate for vapor-phase synthesis of a single crystal diamond film according to the present invention is 1 ° to 3 ° from the (111) crystal plane.
It is characterized by having a silicon substrate having an inclined surface and a platinum single crystal film coated on the silicon substrate.

Further, another substrate for vapor phase synthesis of a single crystal diamond film according to the present invention is one substrate from the (0001) crystal plane.
It is characterized by having a sapphire substrate having a surface inclined by 3 ° to 3 °, and a platinum single crystal film coated on the sapphire substrate.

Further, another substrate for vapor phase synthesis of a single crystal diamond film according to the present invention is one substrate from the (0001) crystal plane.
It has a quartz substrate having a surface inclined at an angle of 3 ° and a platinum single crystal film coated on the quartz substrate.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a platinum single crystal substrate having a surface inclined by 1 ° to 3 ° from the (111) crystal plane, and a silicon having a surface inclined by 1 ° to 3 ° from the (111) crystal plane are described. A substrate comprising a substrate and a platinum single crystal film coated on the silicon substrate, 1 ° to 1 ° from the (0001) crystal plane
A substrate composed of a sapphire substrate having a surface inclined by 3 ° and a platinum single crystal film coated on the sapphire substrate, or a quartz substrate having a surface inclined by 1 ° to 3 ° from the (0001) crystal plane, and the quartz substrate A single-crystal diamond film is formed by vapor-phase synthesis using a substrate composed of a platinum single-crystal film coated on a substrate.

A platinum single crystal substrate having a surface inclined by 1 to 3 degrees from the (111) crystal plane will be described below.
Similar effects can be obtained by using other substrates.

When the surface (off-cut surface) inclined by 1 ° to 3 ° instead of the (111) crystal plane (just plane) is used for the substrate, the crystallinity of the fused portion of the diamond film surface does not decrease, and The generation of crystals is suppressed. This mechanism is considered as follows.

When a diamond film is formed using the off-cut surface of a platinum single crystal as a substrate, a crystal structure called a step and a kink as shown in FIG. 1 exists on the surface. These crystal structures serve as clues for epitaxial growth (lattice arrangement reflecting the crystal lattice arrangement on the substrate surface) and improve the degree of orientation matching of the diamond film. As a result, it is possible to suppress a decrease in the crystallinity of the fused part of the (111) plane of the diamond film synthesized by the vapor phase.

On the other hand, when the (111) just surface is used for the substrate, such a surface structure does not exist as shown in FIG. In this case, the orientation of the diamond fluctuates due to no clue to the epitaxial growth, and the degree of matching is limited. As a result, the diamond (111)
The crystallinity decreases at the fusion part of the plane.

FIG. 3 schematically shows a cross-sectional structure of a diamond film surface when an off-cut surface is used as a substrate. As shown in FIG. 3, when the off-cut surface is used as a substrate, the growth proceeds two-dimensionally due to the presence of diamond steps and kinks on the surface of the diamond film. , Aligned in the off-angle direction. For this reason, generation of twins is suppressed.

On the other hand, when the just surface is used for the substrate,
As shown in FIG. 4, the growth of the diamond film proceeds two-dimensionally. In this case, there occurs a case where (111) planes having different crystal arrangements are fused, and as shown in FIG. Twins are formed.

As described above, the use of the off-cut plane prevents fusion of the (111) planes and the formation of twins, but such an action is universally applied to all the off-cut planes. is not. As a result of experimental research by the present inventors, it has been found that the above-mentioned effects can be obtained by setting the offset angle to 1 ° to 3 °. If the offset angle is larger than 3 °, the step interval becomes smaller, and it becomes difficult to obtain the above effects. Further, when the offset angle increases, another crystal plane appears.

The above-mentioned effects obtained by using the off-cut surface of the platinum single crystal cannot be expected at all according to technical common sense. The use of an off-cut surface for a substrate for epitaxial growth of a thin film is itself a well-known means of improving crystallinity. However, in the case of the present invention, the surface of the substrate is previously damaged with diamond powder having a particle size of 15 to 30 microns. , The surface crystal structure is destroyed,
According to common sense, the effect of the off-cut surface cannot be expected. As described above, even when the substrate surface is damaged, it is generally impossible to improve the crystallinity of the single crystal diamond by using the off-cut surface.
However, according to the idea of the present inventors, the above-described excellent effects can be obtained by the constituent elements of the present invention.

[0022]

Next, examples of the present invention will be described in comparison with comparative examples.

[Example 1] A diameter of 10 mm and a thickness of 2 m
A single-crystal platinum substrate having a size of m and having a (111) crystal plane is set in a reactor, and the inside of the reactor is evacuated. Then, the inside of the reactor was maintained at 50 to 60 Torr. Thereafter, microwave plasma is generated, and the substrate temperature is 875 ° C.
It was made to become. The substrate temperature was measured from above the reactor using a radiation thermometer. When synthesis was performed for 5 hours in this manner, granular diamond having a uniform crystal orientation was precipitated.
When the gas phase synthesis was continued for further 35 hours under the same conditions, adjacent granular diamonds were fused to form a continuous single crystal diamond film having a (111) crystal plane.

Next, the dependence on the offset angle was examined. <1
12> direction 1 °, 2 °, 3 °, 4 °, 5 °, 6 °, 7
The same experiment as described above was performed using the surface inclined at 8 °, 8 °, 9 °, and 10 ° as a substrate. In each case, a diamond film having a (111) crystal plane was obtained. The orientation matching and the twin ratio of these samples were measured by X-ray diffraction. The results are shown in FIGS. 1 ° inclination from (111) plane
In the case of ３3 °, the half-width of X-ray diffraction and the ratio of twins are smaller than those of the just plane, and it can be seen that there is an effective effect.

Example 2 A silicon wafer having a (111) crystal plane was cut off in the range of 0 ° to 10 ° in the same manner as in Example 1, and a platinum thin film of 10 μm was formed by magnetron sputtering. Deposited in thickness. The substrate temperature during vapor deposition was kept at 800 ° C. When the platinum film was evaluated by X-ray diffraction, it was confirmed that the platinum film had an epitaxial relationship with silicon and was a single crystal. When such a platinum / silicon substrate was used to synthesize diamond in the same manner as in Example 1, a single-crystal diamond film having a (111) crystal plane having an epitaxial relationship with the substrate was formed. As a result of evaluating the sample obtained by X-ray diffraction, it was found that the half-width of X-ray diffraction and the ratio of twins were smaller than those of the just plane when the off angle was 1 ° to 3 °. Was.

Example 3 Sapphire having a (0001) crystal plane was cut off from 0 ° to 10 ° in the same manner as in Example 1 to form a substrate, and a platinum thin film of 1 μm was deposited by magnetron sputtering. did. The substrate temperature during vapor deposition was kept at 600 ° C. When the platinum thin film was evaluated by X-ray diffraction, it had an epitaxial relationship with sapphire.
It was confirmed that the film was a single crystal film. Diamond was vapor-phase synthesized using such platinum / sapphire as a substrate. A mixed gas of hydrogen and carbon monoxide containing 2.0% of carbon monoxide gas was supplied, and the inside of the reactor was maintained at 60 Torr. afterwards,
Microwave plasma was generated and the substrate temperature was set to 920 ° C. When synthesis was performed for 3 hours in this manner, granular diamond having a uniform crystal orientation was precipitated. When the gas phase synthesis was continued for further 10 hours under the same conditions, the adjacent granular diamonds were fused to form a continuous single-crystal diamond film having a (111) crystal plane. As a result, a single-crystal diamond film having a (111) crystal plane having an epitaxial relationship with the plate was formed. As a result of evaluating the obtained sample by X-ray diffraction, the off-angle was also 1 ° in this case. In the case of ３3 °, the half-width of X-ray diffraction and the ratio of twins were smaller than those of the just plane, and it was confirmed that there was an effect.

Example 4 Quartz having a (0001) crystal plane was cut off in the range of 0 ° to 10 ° as in Example 1 as a substrate, and a platinum thin film of 3 μm was deposited by magnetron sputtering. did. The substrate temperature during vapor deposition was kept at 700 ° C. When the platinum thin film was evaluated by X-ray diffraction, it was confirmed that the platinum thin film had an epitaxial relationship with quartz and was a single crystal film. When diamond was vapor-phase synthesized using platinum / quartz as a substrate in the same manner as in Example 3, a single-crystal diamond film having a (111) crystal plane having an epitaxial relationship with the substrate was formed. As a result of evaluating the obtained sample by X-ray diffraction, the half-width of X-ray diffraction and the ratio of twins are smaller than those of the just plane when the off-angle is 1 ° to 3 °. Was confirmed.

[0028]

As described above, according to the present invention,
A high-quality single-crystal diamond film with few crystal defects such as twins can be formed without lowering crystallinity at a fusion portion between (111) crystal planes. As described above, the present invention makes it possible to synthesize a high-quality single-crystal diamond film in a gas phase. Makes a significant contribution to the advancement of this type of technology.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing the growth of a diamond film on a platinum off-cut surface, showing that a step-kink structure is a key to epitaxial growth.

FIG. 2 is a schematic view showing the growth of a diamond film on a platinum just surface, showing that there is less clue for epitaxial growth as compared with an off-cut surface.

FIG. 3 is a cross-sectional view of a diamond film surface portion when an off-cut surface is used as a substrate, and shows that the growth directions are aligned with the offset angle direction.

FIG. 4 is a cross-sectional view of a diamond film surface portion when a just surface is used as a substrate.

FIG. 5 is a schematic view showing twins in a (111) oriented diamond film, which is formed at a fusion portion of (111) oriented diamond films having different lamination patterns.

FIG. 6 is a graph showing the dependence of the X-ray diffraction half width on the platinum substrate offset angle.

FIG. 7 is a graph showing the dependence of the twinning ratio on the platinum substrate offset angle.

Claims (8)

[Claims] 1. A method for forming a single-crystal diamond film, wherein a single-crystal diamond film is vapor-phase synthesized using a platinum single-crystal substrate having a surface inclined by 1 ° to 3 ° from a (111) crystal plane. . 2. A single crystal diamond film is vapor-phase synthesized using a substrate in which a platinum single crystal film is coated on a silicon substrate having a surface inclined by 1 ° to 3 ° from a (111) crystal plane. Method for forming a single crystal diamond film. 3. A single crystal diamond film is vapor-phase synthesized using a substrate in which a platinum single crystal film is coated on a sapphire substrate having a surface inclined by 1 ° to 3 ° from a (0001) crystal plane. Method for forming a single crystal diamond film. 4. A single crystal diamond film is vapor-phase synthesized using a substrate in which a platinum single crystal film is coated on a quartz substrate having a surface inclined by 1 ° to 3 ° from a (0001) crystal plane. Method for forming a single crystal diamond film. 5. A single crystal diamond film vapor phase synthesis substrate comprising a platinum single crystal substrate having a surface inclined by 1 ° to 3 ° from a (111) crystal plane. 6. A single-crystal diamond film vapor phase comprising: a silicon substrate having a surface inclined by 1 ° to 3 ° from a (111) crystal plane; and a platinum single-crystal film coated on the silicon substrate. Substrate for synthesis. 7. A single crystal diamond film vapor phase comprising: a sapphire substrate having a surface inclined by 1 ° to 3 ° from a (0001) crystal plane; and a platinum single crystal film coated on the sapphire substrate. Substrate for synthesis. 8. A single-crystal diamond film vapor phase comprising: a quartz substrate having a surface inclined by 1 ° to 3 ° from a (0001) crystal plane; and a platinum single-crystal film coated on the quartz substrate. Substrate for synthesis.