JPS60231498A - Synthesizing method of diamond under low pressure - Google Patents

Abstract

PURPOSE:To suppress the formation of silicon carbide and to grow diamond effectively by allowing hydrogen of exited state of react with gaseous hydrocarbon in a reaction vessel of low pressure and bringing the formed hydrocarbon radical into contact with a substrate. CONSTITUTION:Gaseous hydrogen 10 introduced into a reaction tube 14 of a low pressure (a mark 9 shown a vacuum pump) is exited with microwave charged via a wave guide 15 from a generator 5 to form hydrogen plasma 12. Then, in the downstream side lower than the generation place of the hydrogen plasma, gaseous methane 11 is introduced into the reaction pipe 14 from a feed pipe 16 and allowed to react with the hydrogen plasma to form hydrocarbon radical (methyl, methylene, methine). Next, the hydrocarbon radical is adsorbed on a substrate 3 (silicon wafer or the like) being heated at about 600-1,100 deg.C with a heater 13 to grow diamond. (Still more, since the graphite formed simultaneously is easily brought to react with the exited hydrogen atom or hydrogen molecule, it is changed into methane and automatically removed.)

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a method for depositing diamond on a substrate such as a semiconductor.

[Background of the invention]

Diamond is known as the hardest material, but it is also an electrically high insulator (specific resistance 1).
012Ω・crn) but is a good conductor of heat (six times that of copper at room temperature), is transparent to a wide range of light ranging from ultraviolet to infrared, and is chemically stable. It has excellent properties as a material.

Diamond is currently synthesized primarily by the cylinder pressure method. The high-pressure method is a method of synthesizing by crystal transition of graphite at a high temperature of 1500° C. or higher and a high pressure of 60,000 atmospheres or higher. Particulate diamond can be synthesized by this method,
These are used in abrasives, tools, etc.

In contrast, a low-pressure method has recently been demonstrated that allows diamond to be synthesized even under low-pressure conditions of 1 atmosphere or less (see note below).

The low-pressure method makes it possible to synthesize not only particles but also film-like diamonds, and a wide range of applications can be considered. One of them is its application to heat dissipation substrates for semiconductor devices. As ICs become more highly integrated, semiconductor devices are becoming three-dimensional, but this requires an insulating material that not only connects the semiconductor elements but also quickly transfers the heat generated by the elements to the outside. Membrane is best.

(Note) (1) Handout of Nobuo Setaka's report on "Low-pressure gas phase synthesis technology for diamond films" at the Science and Technology Agency's Inorganic Materials Research Institute at a briefing session on low-pressure diamond synthesis sponsored by the New Technology Development Corporation on October 5, 1985. (2) Kamo Raw Materials, Institute for Inorganic Materials, Science and Technology Agency, at the Japan Society of Applied Physics on April 4, 1983;
Nobuo Setaka presented “Synthesis of film-like diamond by microwave plasma method”, lecture proceedings, page 215 (31 Japanese Journal of Ap
Plied Physics.

vol, 21. A4, April 1982.
pp, L183-L185 Figure 2 shows the diamond low-pressure synthesis technology that has already been announced. A mixed gas 1 of methane (at a concentration of 5% to several %) and remaining hydrogen is supplied to a reaction tube 2. The pressure in the reaction tube 2 is reduced to several tens of Torr by vacuum=e7f9. The waveform of the microwave generated by the microwave oscillator 5 is adjusted by the isolator 6, and the waveform is adjusted by the isolator 6.
After the output is measured, it is sent to the reaction tube 2 through the waveguide 15. The above-mentioned mixed gas of methane and hydrogen is turned into plasma by this microwave, and the excited carbon generated by its decomposition is transferred to the silicon urethane on the pedestal 4 in the reaction tube 2.
Diamond crystals are deposited on a substrate 3 such as the like. The exhaust gas is exhausted to the outside of the system by a vacuum pump 9. During the above reaction, the silicon substrate 3 is heated to 00 to 900 DEG C. by methane-hydrogen plasma.

According to the above method, it is possible to synthesize diamond particles or films with a diameter or thickness of several μm in a few hours.However, since methane and hydrogen are simultaneously plasma decomposed, carbon radicals are produced in addition to hydrogen radicals and water bulk ions. , carbon ions are also generated, and silicon carbide is likely to be generated when a substrate such as a silicon wafer is etched, scraped, or tarred.

For this reason, the excited carbon, which serves as the crystal nucleus for diamond formation, is consumed and the growth of diamond is inhibited.

[Purpose of the invention]

The present invention has been made to improve the drawbacks of the previously proposed techniques described above, and its purpose is to provide a low-pressure diamond synthesis method that suppresses the formation of silicon carbide and efficiently grows diamond. .

[Summary of the invention]

The low-pressure diamond synthesis method of the present invention involves decomposing only hydrogen gas into plasma in a low-pressure reaction vessel to remove excited hydrogen atoms such as hydrogen radicals, and then bringing hydrocarbons into contact with the excited hydrogen atoms. The hydrocarbon radicals are then decomposed to generate hydrocarbon radicals, which are adsorbed onto a substrate such as a silicon wafer, and the remaining hydrogen atoms in the hydrocarbon radicals are separated by thermal decomposition. It is what produces diamonds.

[Embodiments of the invention]

FIG. 1 shows an example of an apparatus used to carry out the present invention.

Hydrogen gas 10 is introduced above the reaction tube 14.

This hydrogen gas is excited by microwaves transmitted from the microwave oscillator 5 in the reaction tube 14 as shown in FIG. 2, and generates hydrogen plasma 12.

On the other hand, on the downstream side of this hydrogen plasma generation surface,
Methane gas 11 enters the reactor 14 through the methane supply pipe 16 without being converted into plasma.

This methane gas reacts with the above-described excited hydrogen atoms above the substrate 3 such as a silicon wafer, and hydrogen, which is a constituent element of methane, is partially removed to generate hydrocarbon radicals such as methyl, methylene, and methine. Cholera hydrocarbon radical is
After being adsorbed to the substrate 3 such as a silicon wafer, the heater 13
Hydrogen atoms remaining in these hydrocarbon radicals are further removed by heating or by the action of excited hydrogen atoms, etc., to form crystal nuclei of diamond or graphite.

Among these crystal nuclei, graphite crystal nuclei easily react with excited hydrogen atoms or hydrogen molecules such as radicals, so they selectively react with them to generate methane and are removed, and only diamond grows on the substrate 3.

Hereinafter, specific examples of the present invention will be described.

[Example 1] Using an apparatus configured as shown in Fig. 1, in which a quartz glass tube with an inner diameter of 130% and a length of 300 wR was provided with hydrogen and methane supply pipes, only hydrogen was turned into plasma as described above, and the substrate was placed under a heater. A diamond precipitation experiment was conducted using a heating method. A silicon wafer with an [oO:] plane was used as the substrate. Table IK shows the experimental conditions.

Table 1 Experimental conditions Pressure is 5 Torr increments, substrate temperature is 100' increments,
Experiments were conducted by changing the time in lhr increments. The microwave power was 40W or 100W.

When the silicon wafer surface was observed using SEM after the completion of the actual #, angular precipitates with a diameter of approximately 1 μm were seen as shown in Figure 3. (Figure 3 shows the reaction time of 3 hours)
. Although the shape and size of the precipitate varied depending on the precipitation conditions, the precipitate was obtained in all cases within the range of the experimental conditions shown in Table 1. The distance between the planes of the crystal determined by analysis of the electron diffraction image of the precipitate coincides with the distance between the planes of cubic diamond, and the precipitate is determined to be diamond.

In addition, when the precipitation time was increased (6 hr), it was observed that the particulate precipitates coalesced into a film as shown in FIG. In addition, when the temperature exceeds 1000℃, the speed of diamond folding becomes extremely slow, and below 600℃,
It was confirmed that graphite did not precipitate into diamond.

[Example 2] When an experiment was conducted under the same conditions using the same equipment as in Example 1 and using ethane or zolonone instead of methane, diamond precipitation was observed as in Example 1.

[Comparative Example 1] For comparison, a silicon wafer of 1/iC5tmn x 5yen was prepared using a quartz glass tube with an inner diameter of 13mm and a length of 200mm.
A diamond precipitation experiment was conducted using the conventional method shown in FIG. 2, that is, the method of simultaneously plasma decomposing a mixed gas of methane and hydrogen.

The experimental conditions are shown in Table 2. Table 2 Experimental conditions After the experiment was completed, the silicon wafer surface and reaction tube wall were analyzed by electron beam diffraction, and a strong diffraction image of silicon carbide was obtained. No diffraction image corresponding to diamond was obtained within the range of experimental conditions shown in .

Further, as a result of observation of the surface of the silicon wafer by SEM (scanning electron beam), severe etching marks were observed.

〔Effect of the invention〕

According to the method of the present invention, diamond can be efficiently deposited on a substrate such as a silicon wafer while suppressing the deposition of silicon carbide or the like.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the apparatus used in the low-pressure diamond synthesis method of the present invention, Fig. 2 is a schematic diagram of the apparatus used in the previously proposed diamond low-pressure synthesis method, and Figs. 3 and 4 are the embodiments of the present invention. This is an SEM photograph of the diamond obtained by this method. 2... Reaction tube 3... Silicon wafer 4... Pedestal 5... Microwave oscillator, 9... Vacuum bonder l
O...Waveguide 13...Heater Figure 1, Figure 2, Figure 3, Figure 4 and wide procedural amendment (method) February 1980, 29 [Showa! 9th Patent Application No. P〆) No. 3 Person making the amendment I1c Person in charge of any one of the following: Applicant 4, Agent Address: 3308IIIBG, Chisu Building, Marunouchi, 2-6-2, Marunouchi, Chiyo F Tsuki-ku, Tokyo. Before the 2nd one! Explanation column 8 Contents of amendment Six amendments to attached sheet The following matters in the specification of the application will be amended. In the first part of the record, it says, ``This is a SIIEM photo of a diamond.'' [
Scanning electron microscope (S
EM) This is a photograph. ” he corrected.

Claims (1)

[Claims] 1. Hydrogen gas is brought into a plasma state in a low-pressure reaction vessel, and a separately prepared hydrocarbon gas that releases carbon by decomposition is mixed with the hydrogen gas in the plasma state to produce the carbonized gas. Hydrocarbon radicals are generated by removing hydrogen from hydrogen, and the hydrocarbon radicals are brought into contact with a substrate heated to 600°C to 1000°C in the reaction vessel to deposit diamond on the substrate. Diamond low pressure synthesis method. 2. The low-pressure diamond synthesis method according to claim 1, wherein the hydrocarbon is methane, ethane, or 4-C.