KR100411710B1 - Apparatus and method for the synthesis of the diamond with powder shape by chemical vapor deposition (cvd) method - Google Patents

Abstract

The present invention relates to a method for synthesizing diamond powder by vapor phase chemical vapor deposition (CVD). In the present invention, the substrate is placed at the edge of the plasma which is not in direct contact with the plasma in the vapor phase chemical vapor deposition diamond synthesis method, thereby inducing homogeneous nucleation at this portion, thereby synthesizing the diamond spherically. The size of the spherical diamond powder synthesized in this method can be controlled to a size of several tens of nanometers in diameter. In addition, it is possible to synthesize diamond powder in large quantities due to the change in the structure of the synthesis apparatus.

Description

Apparatus for synthesizing spherical diamond powder by vapor chemical vapor deposition and spherical diamond synthesizing method using the same {{PARAMETER AND METHOD FOR THE SYNTHESIS OF THE DIAMOND WITH POWDER SHAPE BY CHEMICAL VAPOR DEPOSITION (CVD) METHOD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing spherical diamond powder, and more particularly, in a chemical vapor deposition (CVD) method in which diamond is formed on a film using plasma, the plasma is in direct contact with the diamond. In addition to the substrates to be synthesized, another substrate (s) relates to a method in which diamonds can be synthesized in the form of spherical powder rather than in the form of films by placing them around plasma which is not in direct contact with the plasma.

Diamond is one of the hardest materials in existence, and diamond powder has been used for a long time as an abrasive added to abrasive oil to increase the polishing rate when polishing oxide-based and hard materials. The particle size of the diamond powder used for this purpose is from several nm to several tens of micrometers. The particle size of the diamond has a great influence on the surface roughness of the polished material. In the case of lepping where the roughness corresponds to rough polishing of several tens of micrometers, diamond powders of several to several tens of micrometers are used, and the surface irregularities of the material In the case of mirror polishing where this tens of nm is required, a diamond powder of several micrometers or less is used.

In the production of such abrasive diamond powder, conventionally synthesized by iii) explosive method (method of synthesizing diamond by mixing explosive powder and solid raw graphite in an airtight container), or ii) high temperature. Dozens to hundreds of micrometers synthesized in the high pressure and high temperature (HPHT) method, a method of synthesizing diamond using 50,000 graphite and solid graphite as a raw material and metal as a catalyst) Methods of crushing diamonds of size have been used. However, diamond powders produced by these two methods have irregular particle shapes due to fabrication techniques. When diamond having such irregular shape is used as an abrasive, there is a problem in that the abrasive can be scratched, which is inappropriate for polishing the surface roughness with a superhard surface of several nm or less. Therefore, in order to overcome this problem, an oxide-based or metal powder other than diamond powder may be used as the superabrasive abrasive, in which case a new polishing process is added and the polishing rate is lowered.

On the other hand, in the case of the chemical vapor deposition (CVD) method of producing diamond on a polycrystalline film, diamond can be synthesized in various forms including spherical shape by controlling the synthesis conditions in the particle formation step. Not only is it difficult to recover because the diamond particles are stuck on the substrate, but when the diamond particles are synthesized by overlapping one or more layers, a problem arises in that a film is formed and the amount that can be recovered is very small. Therefore, in the conventional general CVD method, it is impossible to synthesize a diamond in powder form that can be used as an abrasive.

The present invention has been made to solve the above problems, and provides a method for synthesizing diamond powder having a small particle size of several micrometers or less and spherical particle shape using CVD diamond synthesis method, and also the structure of the synthesis apparatus The purpose of the present invention is to provide a device capable of synthesizing diamond powder in large quantities by remodeling.

Fig. 1 shows an example of the apparatus for synthesizing a diamond film by vapor chemical vapor deposition.

FIG. 2 shows the position at which the spherical diamond powder synthesizing apparatus and spherical diamond are synthesized in the diamond synthesizing apparatus of FIG. 1.

Figure 3 shows a powder photograph of the diamond synthesized in the position of FIG.

FIG. 4A shows a front schematic view of an apparatus that can increase the area where spherical diamond powders are synthesized using a ring shaped substrate using the plasma shown in FIGS. 1 and 2.

FIG. 4B shows a top schematic view of FIG. 4A.

FIG. 5A is a front schematic diagram of a device capable of increasing the area where spherical diamond powders are synthesized by separating plasma into several as in the DC power plasma chemical vapor deposition diamond synthesis method using seven cathodes as a diamond synthesis method [1]. will be.

5B shows a top schematic view of FIG. 5A.

(Description of symbols on the main parts of the drawings;

1: vacuum vessel, 2: plasma, 3: substrate I, 4: diamond film, 7: spherical diamond powder, 8: substrate II.)

In order to achieve this object, according to the present invention, in the CVD diamond synthesis method, it was invented that the diamond is synthesized in the form of a multi-layered powder, not in the form of a film, under a certain condition of the edge of the plasma. The present invention takes advantage of the fact that the driving force for diamond nucleation is large at the edge of the plasma, so that the substrate meets the conditions of homogeneous nucleation, which nucleates in the gas phase. The present invention provides a method for producing a large amount of diamond powder by synthesizing spherical diamond powder, and separating plasma by the number of substrates by varying the number of substrates, thereby increasing the area in which diamond can be synthesized in powder form in the gas phase.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

Fig. 1 shows an example of a diamond synthesizing apparatus by vapor phase synthesis, in which diamond is grown in a film form 4 on a substrate I (3) in contact with a plasma 2 in a vacuum vessel 1. The substrate I is placed on the substrate holder 6 cooled by the cooling water 5 circulated. The main synthesis parameters for diamond synthesis using this synthesizer include gas composition, pressure and substrate temperature, which should be controlled to 1-20% CH ₄ , 10-200 Torr and about 1000 ° C in hydrogen gas, respectively. Synthesis of spherical diamond powder is possible. However, as described above, when synthesizing spherical diamond powder using such a device, diamond particles are stuck on the substrate and are difficult to recover, and when diamond particles are synthesized by overlapping one or more layers, a film is formed and recovered. There is a problem that the amount can be very small.

FIG. 2 shows a spherical diamond powder synthesized by vapor phase chemical vapor deposition shown in FIG. 1 in which a substrate II (8) is additionally provided in addition to the substrate I (3) in contact with plasma. It shows a diamond synthesizer. In the spherical diamond synthesizing apparatus according to the present invention, a spherical diamond powder can be synthesized by additionally installing a substrate II (8) located around the substrate I and not in contact with the plasma in addition to the substrate I. At this time, the spherical diamond powder 7 is synthesized on a ring-shaped substrate II 8 that is not in contact with the plasma located around the substrate I. As described above, since the driving force of diamond nucleation is large at the edge portion of the plasma and satisfies the conditions for uniform nucleation in nucleation in the gas phase, spherical diamond powders, not films, are synthesized on the substrate II mounted at the plasma edge. do.

FIG. 3 shows spherical diamonds synthesized on the substrate II using the diamond synthesizing apparatus as shown in FIG. Accordingly, the present invention provides a spherical diamond powder synthesizing apparatus including a substrate II which does not contact plasma around the substrate I in addition to the substrate I of the existing diamond synthesis apparatus as shown in FIG. 2, and a spherical diamond powder synthesis method using the same.

4A and 4B show the front and top schematic views of the apparatus for remodeling the substrate portion of the diamond synthesizing apparatus as shown in FIG. 2 to synthesize a large amount of spherical diamond powder. According to this apparatus, by arranging the substrate I in contact with the plasma in a ring form, a portion which does not contact the plasma as well as the outside of the ring-shaped substrate I is formed, thereby increasing the area not in contact with the plasma. 4A and 4B show an apparatus for synthesizing spherical diamond powder formed by mounting substrate II on a portion of the ring-shaped substrate I which is not in contact with the plasma inside and outside the ring-shaped substrate I. When the diamond is synthesized using this apparatus, the spherical diamond powder can be synthesized not only outside of the ring-shaped substrate I but also inside, so that the spherical diamond powder can be synthesized in large quantities. Accordingly, the present invention provides a spherical diamond powder synthesizing apparatus for synthesizing a large amount of spherical diamond powder by specifically setting the shape of the substrate, and a spherical diamond powder synthesizing method using the same.

5A and 5B illustrate a diamond synthesis apparatus using a vapor chemical vapor deposition method in which plasmas are separated by the number of substrates when the number of substrates is changed, and a plurality of substrates may be used to increase the synthesis area of the spherical diamond powder. Front and top schematic views of the device are shown. In the present invention, when two or more substrates I are used, plasma is separated into two or more, and the diamond powder is synthesized on the substrate II mounted around each substrate I, so that the synthetic area of the diamond powder is increased, thereby increasing the amount of diamond powder. You will get For example, in the case of a multi-cathode DC PACVD (PAC) apparatus using seven cathodes, the plasma is subjected to the number of substrates I as shown in the plan view in FIG. The cathode structure of the next pole DC power plasma chemical vapor deposition apparatus using 7 cathodes is radially located with six cathodes spaced at 60 ° with respect to one cathode as shown in FIG. 5B. By dividing the plasma by the number of cathodes and placing the substrates I and II respectively, the area of synthesis of the spherical diamond powder can be effectively increased, and the synthesis of a large amount of the spherical diamond powder is possible. For more details on the next pole DC power plasma chemical vapor deposition apparatus Therefore, the present invention provides a spherical diamond powder synthesizing apparatus for synthesizing a large amount of diamond powders by increasing the area where spherical diamond powders are synthesized by installing two or more substrates, and spherical diamonds using the same. Provide a synthesis method.

In the method of synthesizing spherical diamond using the diamond synthesis apparatus of Figs. 2, 4A, 4B, 5A, and 5B, the position of the spherical diamond is measured in relation to the temperature of the substrate even in one copper ring. Since the temperature is different, it is impossible to accurately measure the temperature at which spherical diamond is synthesized in each synthesis. One thing is certain, however, that the temperature of substrate II, which is not in direct contact with the plasma in general, is lower than the temperature of the substrate I, which is in contact with the plasma where the diamond synthesis on the film is made (about 1000 ° C.) and higher than room temperature (25 ° C.). Therefore, it is possible to synthesize spherical diamond powder having a uniform particle size of fine grains of several micrometers or less on the substrate II even at relatively low temperatures in the range of 25 ° C to 1000 ° C. The temperature of the substrate at which the diamond is synthesized determines the rate at which spherical diamond is synthesized. If the temperature is low within the above temperature range, the synthesis rate is slowed down, and if the temperature is high, the synthesis rate is high.

On the other hand, as can be seen from Fig. 2, the place where spherical diamond is synthesized is isolated from the plasma, and the density of the spherical diamond to be synthesized is inversely proportional to the distance from the plasma. That is, as the distance from the plasma decreases, the density of the spherical diamond powder synthesized decreases, and when more than a predetermined distance, the spherical diamond is not synthesized. As can be seen in Example 3, when the synthesis of diamond is performed at a position about 10 cm away from the plasma, spherical diamond is not synthesized. Therefore, the position at which the diamond is synthesized should be isolated from the plasma and at the same time not separated from the plasma by more than 10 cm.

Hereinafter, the present invention will be described in more detail with reference to specific examples, but the scope of the present invention is not limited to the following examples.

<Example 1>

Using a plasma formed in the next pole DC power plasma chemical vapor deposition apparatus, a ring-shaped substrate II of 80 mm in diameter and 110 mm in diameter and 5 mm in thickness was placed around a Mo substrate I with a diameter of 76 mm and a thickness of 10 mm (see Fig. 2). ), The methane composition was 8%, the power was 15 kW, the temperature of the copper ring-type substrate II was 600 ℃, and the synthesis experiment was performed for 100 hours. As a result, spherical diamonds as shown in Fig. 3 were synthesized on the copper ring-shaped substrate II in several layers.

<Example 2>

Spherical diamond powder was synthesized in the same apparatus as in Example 1 (see FIG. 2). Synthesis conditions were methane composition 8%, pressure 200 Torr, gas flow rate 200 sccm. At this time, spherical diamond powder as shown in Fig. 3 was synthesized on the substrate II of Fig. 2. The particles of each synthesized diamond powder were in the form of a powder having a diameter of about 0.5 μm and synthesized in multiple layers.

<Example 3>

In the same apparatus as in Example 1 (see Fig. 2), the outer diameter of the substrate II was set to 30 cm (inner diameter is the same as that of Example 1), and the density distribution with distance from the plasma of the diamond powder heaped on the substrate II was examined. Synthesis conditions were the same as shown in Example 1. The density of the diamond powder synthesized on the substrate II was almost the same as that of FIG. 3 up to 1 cm away from the plasma side, but the density of the synthesized diamond powder decreased toward the edge direction, that is, away from the plasma. At about 10 cm away, the density of the synthesized diamond powder was nearly zero. Therefore, it can be seen that the position where the diamond powder can be synthesized is a position within a distance of about 10 cm from the plasma.

The present invention provides a spherical diamond synthesizing apparatus capable of synthesizing spherical diamond powder having a diameter of several micrometers or less by vapor phase synthesis method, and a spherical diamond synthesizing method using the same and a structure of the diamond powder synthesizing apparatus. Provided are a device capable of synthesizing in large quantities and a diamond synthesis method using the same. Such fine diamond can be applied not only to the abrasive used for high quality high speed polishing having surface irregularities of about several nm, but also to electrode materials of field emission display (FED), diamond micro tool fabrication, and the like.

Claims (5)

In a vapor chemical vapor deposition diamond synthesizing apparatus, in which a plasma is formed in a vacuum vessel to decompose a carbon source reaction gas to synthesize diamond on a substrate. A spherical diamond powder synthesizing apparatus comprising a substrate II arranged not to be in direct contact with the substrate. 2. The spherical diamond powder synthesizing apparatus according to claim 1, comprising a substrate I fabricated and provided in a ring form and a substrate II provided inside and outside the ring form substrate I so as not to contact plasma. The spherical diamond powder synthesizing apparatus according to claim 1, comprising at least two substrates I for separating the plasma into two or more substrates and a substrate II arranged so as not to contact the plasma. The spherical diamond powder synthesizing apparatus according to any one of claims 1 to 3, wherein the substrate II is disposed within 10 cm of the plasma without being in contact with the plasma. The vapor deposition method for synthesizing diamond on the substrate I by forming a plasma in a vacuum vessel and decomposing a carbon source reaction gas, wherein the diamond synthesis method comprises any one of claims 1 to 3 including substrate I and substrate II. A spherical diamond powder synthesizing method comprising the step of synthesizing spherical diamond powder on a substrate II by using the spherical diamond powder synthesizing apparatus according to one of claims 1 to 25, and the temperature of the substrate II.