JPS6355196A - Production of diamond having high heat-conductivity - Google Patents

Abstract

PURPOSE:To produce a diamond having high thermal conductivity at a high rate of production using a vapor growth process under low temperature and pressure condition, by specifying the relative amounts of acetone and hydrogen in a reaction gas, pressure of the reaction gas, distance between a substrate and a heater and temperature of the heater. CONSTITUTION:A reaction gas containing acetone and hydrogen is introduced into a reaction vessel and thermally decomposed to effect the growth of diamond crystal on the substrate. In the above process, the volume ratio of acetone/ hydrogen is adjusted to (2-3)/100 and the pressure of the reaction gas is set to 10Torr-10atm. The distance between the substrate and the heater is <=5mm and the temperature of the heater is >=2,250 deg.C. A diamond having excellent thermal conductivity can be quickly produced on an industrial scale under the above conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a method for producing diamond with high thermal conductivity at high speed.

(Prior art) Diamond has the highest hardness and thermal conductivity among currently known substances, and also has extremely high modulus of elasticity, compressive strength, and electrical insulation, and is transparent and chemically resistant. It is a stable substance. Therefore, taking advantage of its excellent characteristics,
“Wear-resistant coatings for jigs and tools, protective films for solar cells,
Research is underway to develop applications for optical lenses and heat sinks for semiconductor components. However, natural diamonds are produced in small quantities and are extremely expensive, so they cannot be used as industrial materials.

For this reason, research on the production of artificial diamonds is actively being conducted, but artificial diamonds manufactured by conventional methods under high temperature and high pressure are also expensive and have little usefulness as industrial materials. Moreover, both natural diamonds and artificial diamonds generally have a lumpy or granular shape, and it is difficult to manufacture a film, so that the useful properties of diamond cannot be fully utilized.

For this reason, research has recently been actively conducted to produce diamonds by vapor phase growth at low temperatures and low pressures. The main method is to introduce a mixed gas of hydrogen and an organic compound such as methane, ethylene, acetylene, or acetone onto the surface of a heated substrate, and use the thermal energy of a heating element (thermal filament) close to the substrate to generate the mixed gas. There is a method of thermally decomposing active species to grow diamond on the surface of the substrate (Japanese Patent Publication No. 59-27753, or the proceedings of the 33rd Applied Physics Association Lectures,
1 p-ZD-6, 1986). This method uses low temperature
Since it is carried out under low pressure, it can be realized with relatively small equipment, which is industrially advantageous.

However, so far, in this method, the relationship between the reaction conditions such as gas pressure and heating body temperature and the resulting diamond properties has not been clarified. If the thermal conductivity is small, or if the thermal conductivity is increased, there are problems such as an extremely slow growth rate.

(Problems to be Solved by the Invention) The present invention has been made to solve the above-mentioned problems, and it produces diamond with high thermal conductivity by a vapor phase growth method using a heating body at low temperature and low pressure. The purpose is to provide a method that can be manufactured at high speed.

[Structure of the invention]

(Means and effects for solving the problems) In the method for producing highly thermally conductive diamond of the present invention, a substrate is placed in a reaction vessel, a reaction gas containing acetone and hydrogen is introduced into the reaction vessel, and this When growing diamond on the substrate by heating the reaction gas with a heating element to thermally decompose it, the relative amounts of acetone and hydrogen are in a volume ratio of (acetone)/(hydrogen) = 2/100 to 3/100. This method is characterized in that the pressure of the reaction gas is 10 Torr to 10 atmospheres, the distance between the substrate and the heating element is less than 5 m, and the temperature of the heating element is 2250° C. or higher.

The above reaction conditions were discovered as a result of systematic research into the relationship between various reaction conditions and diamond properties, and under these reaction conditions, diamond with high thermal conductivity is produced at a high rate.

In carrying out the method of the present invention, first, a substrate is placed in a reaction vessel used in a normal vapor phase growth method. Subsequently, a reaction gas containing acetone and hydrogen is introduced. When an organic compound other than acetone is used in place of acetone, the growth rate is low. Also, the relative amount of acetone and hydrogen is (acetone)/(hydrogen) = 2/100 to 3/10 in volume ratio.
0 is desirable. If it is less than 2/100, the growth rate will be low, and if it exceeds 3/100, the formation of non-diamond substances and voids will become predominant, resulting in poor thermal conductivity. Further, the pressure of the reaction gas is preferably 10 Torr to 10 atmospheres. 10T
If the pressure is less than orr, the growth rate becomes extremely low, and if it exceeds 10 atm, graphite is likely to be formed. Next, a heating element close to the substrate is heated. Here, the distance between the substrate and the heating element is desirably less than 5 IIfi, and if it is 5 nm or more, the growth rate will be low. Further, the temperature of the heating body is desirably 2250°C or higher; if it is lower than 2250°C, the growth rate will be low and the thermal conductivity will be poor.

In the above explanation, we have explained the case where the operations are performed in the following order: ■Substrate installation, ■Reaction gas introduction, and ■Heating the heating element.However, the order is not limited to this, and for example, the order of ■ and ■ may be reversed. It's okay.

Note that it is effective to heat the substrate itself to 400° C. or higher because the growth rate of diamond is higher and the thermal conductivity is also improved.

If the reaction gas contains at least one of boron, aluminum, gallium, indium, or thallium, or at least one of nitrogen, phosphorus, arsenic, antimony, or bismuth, semiconductor properties can be improved. High thermal conductivity diamond can be produced at high speed.

Improves heat conduction properties, etc. The electron beam irradiation conditions are no discharge,
In other words, conditions are selected in which gas discharge does not occur, but in practice, the acceleration voltage is 20~aoov and the current density is 5~300.
It is desirable to set it to mA/al. Further, the source of electron beam irradiation is not particularly limited, but a method of irradiating thermoelectrons from a heating body or a method of using an ordinary electron gun are suitable.

According to the method of the present invention as described above, it is possible to produce diamond with good thermal conductivity at a high speed and with less non-diamond components and voids.

(Example) The present invention will be explained in detail below.

Example 1 Silicon was used as a substrate, and diamond was grown on the surface of the substrate as follows. The substrate was placed in a reaction vessel, heated and maintained at 700°C, and then a mixed gas of acetone and hydrogen (volume ratio 2.
5:100) was introduced at a flow rate of 60+aQ/ll1in, and the pressure inside the reaction vessel was reduced to about 30% by exhausting from the gas outlet.
It was maintained at 0 Torr. Next, a heating element made of a tungsten wire with a diameter of 0.1 mm and 30111 points from the base was heated to 2.
It was heated and maintained at 300° C. by direct current heating. As a result, a diamond film with a thickness of 8 mm was formed after 1 hour. When the thermal conductivity of this film was measured at room temperature using the optical alternating current method, it was found to be 14
-1 at 00 Wm-1.

Examples 2 to 7 Examples 2 to 7 according to the present invention are shown in Table 1 together with Example 1.

Comparative Examples 1 to 8 In Comparative Example 1, at least one of the reaction gas composition, the relative amounts of acetone and hydrogen, the reaction gas pressure, the distance between the substrate and the heating element, and the heating element temperature was not within the range of the present invention. -8 in Table 1.

From Table 1, it is clear that according to the method for manufacturing high thermal conductivity diamond of the present invention, high thermal conductivity diamond can be formed at high speed.

〔Effect of the invention〕

As detailed above, according to the method of the present invention, diamond with excellent thermal conductivity can be rapidly produced, and is extremely useful industrially.

Claims (2)

[Claims] (1) A substrate is placed in a reaction vessel, a reaction gas containing acetone and hydrogen is introduced into the reaction vessel, and this reaction gas is heated with a heating element to thermally decompose it, thereby forming diamonds on the substrate. During growth, the relative amount of acetone and hydrogen is (acetone)/(hydrogen) = 2/10 in volume ratio.
0 to 3/100, reaction gas pressure is 10 Torr to 10
A method for producing diamond with high thermal conductivity, characterized in that the atmospheric pressure is low, the distance between the substrate and the heating body is less than 5 mm, and the temperature of the heating body is 2250° C. or higher. (2) The method for producing highly thermally conductive diamond according to claim 1, which comprises irradiating the substrate with an electron beam.