JP6644313B2 - Diamond processing method - Google Patents

Description

  The present invention relates to a diamond processing method, and more particularly to a processing method by an etching process.

Diamond is a hard and chemically stable substance, and one of the substances that is difficult to process.
Therefore, reactive etching (RIE), inductively coupled plasma etching (ICP), and the like have been conventionally used.
These etching methods require dedicated equipment and are expensive, and also have a problem that the diamond surface is greatly damaged by etching.
Patent Document 1 uses a mixed gas composed of an inert gas and a halogen-containing gas, but has the same problem as described above in that it is a plasma etching process.

Japanese Patent No. 5714052

  SUMMARY OF THE INVENTION An object of the present invention is to provide a diamond processing method by etching at a high speed and at a low cost with little damage to the diamond surface.

The diamond processing method according to the present invention includes the steps of forming a film of a metal or metalloid and an alloy or an inorganic compound on a diamond processing portion, and mixing H ₂ O under a mixed gas of an inert gas and H ₂ O or under vacuum. And etching the portion where the film is formed by using the method.
Here, the etching temperature using a mixed gas of an inert gas and H ₂ O or H ₂ O under vacuum is preferably at least 500 ° C. and at an atmospheric temperature equal to or lower than the melting temperature of the film.

In the conventional etching process, a method of masking a non-etched portion is generally used, whereas in the present invention, the surface of diamond has no direct etching action, and a metal or metalloid and its alloy or an inorganic compound film is interposed. The feature is that the diamond in the portion where the film is formed is etched.
Hot gaseous H ₂ O has no direct etching effect on the diamond surface.
However, it has been found by the present inventors that when the above film is formed on a diamond surface and etched with H ₂ O, carbon is dissolved in the film and the diamond surface is etched. .
Examples of such a film include Ni, Co, Cu, Mn, Cr, Fe, V, Mo, Ru, W and alloys thereof, and inorganic compounds thereof. Oxides and carbides are mentioned as examples.
Further, an oxide of Si or an oxide of Al, which is a metalloid, is given as an example.

In the present invention, examples of the inert gas include gases of argon, helium, and nitrogen. The method of mixing H ₂ O is not limited. For example, an inert gas may be charged into water and mixed by bubbling. Alternatively, gaseous H ₂ O may be mixed.
The present invention is characterized in that H ₂ O is reacted for the purpose of promoting solid solution of carbon in a film formed on the surface of diamond.
Therefore, H ₂ O gas may be supplied under vacuum.
For example, a gas in which H ₂ O is mixed while heating the diamond on which the above film is formed in an electric furnace to 500 ° C. to 1500 ° C. (a range where the film does not melt), preferably 700 ° C. to 1100 ° C. It may flow in.
The amount of H ₂ O only needs to contain 0.01% or more in the mixed gas is preferably 0.01% to 30%, more preferably in the range from 0.01% to 5%.
The thickness of the film formed on the surface of diamond is preferably in the range of 1 nm to 1 mm, and more preferably 100 nm to 1 μm, in consideration of the reactivity with H ₂ O.

According to the present invention, the above-mentioned film is formed on a portion where diamond processing is desired to be performed, and the film is formed in a mixed gas atmosphere of an inert gas and H ₂ O at 500 ° C. to 1500 ° C. or in a H ₂ O gas atmosphere under vacuum. Simply by placing it inside, it can be etched through the film.
Therefore, since the etching gas does not directly attack the diamond, there is almost no etching damage, and the etching can be performed at high speed and at low cost.
Further, as will be described in detail later, the anisotropic etching in which the crystal orientation stops at the {111} plane is easy to control the processing.

1 shows a configuration example of an apparatus used for test evaluation of an etching method according to the present invention. (A)-(d) is the schematic diagram which showed the process of the etching process concerning this invention. (A) shows a state in which a Ni film is formed on the surface (100) diamond substrate, (b) shows a state after etching, and (c) shows a state in which the Ni film is removed. This shows a state in which a Ni film pattern is formed on a diamond substrate on the surface (110) at different angles. (A)-(f) show an etching pattern typically. This shows the etching state of the 0 ° Ni pattern. The etching state of the 45 ° Ni pattern is shown.

The method for etching diamond according to the present invention has been evaluated experimentally and will be described below.
FIG. 1 shows an experimental method.
Using N ₂ gas as the inert gas, the N ₂ gas was introduced and bubbled through the water placed in the container, to produce a mixed gas of N 2 _{+ H} 2 _O.
As an etching apparatus, an electric furnace was used to maintain the inside at a predetermined high temperature, and the mixed gas of N ₂ + H ₂ O was flowed into the electric furnace.

<Experiment 1>
FIG. 2 schematically shows the process.
Using a diamond substrate having a (100) surface, the surface was pretreated with a hot mixed acid (concentrated sulfuric acid: concentrated nitric acid = 3: 1), and then a Ni film having a thickness of about 350 nm was formed using a vacuum deposition method in FIG. It was formed as shown in (b).
FIG. 3A shows a photograph of the surface and the shape of the film thickness.
Next, using the experimental apparatus shown in FIG. 1, the diamond on which the Ni film was formed was placed in an electric furnace, and the ambient temperature was set to 900 ° C.
A mixed gas of N ₂ + H ₂ O was flowed into an electric furnace and subjected to etching for 1 hour.
FIG. 2 (c) schematically shows the state, and FIG. 3 (b) shows a photograph of the surface.
It was confirmed that the diamond in the portion where the Ni film was formed was etched.
This is presumed that H ₂ O promoted the solid solution of carbon in the Ni film.
Next, after removing Ni with a hot mixed acid, the surface was washed with dilute nitric acid.
The schematic diagram is shown in FIG. 2 (d), and the photograph is shown in FIG. 3 (c).
The etched shape was a trench structure in which the Ni film portion was deeply excavated, and it was confirmed that the bottom surface was a (100) crystal plane on the {111} side surface.
As shown in FIG. 3 (c), the measurement result is as follows: Etching depth: 31.3 μm
・ Etching rate: 31.3 μm / h
・ Angle θ ₁ : 54.7 °.
For comparison, a diamond substrate similar to the above with a Ni film formed on the surface was placed in an electric furnace and H ₂ gas was allowed to flow. As a result, there was almost no attack on the diamond surface where there was no Ni film. However, the etching rate of diamond in the Ni film portion was as small as 0.43 μm / h.
Similarly, when only N ₂ gas was flowed instead of N ₂ + H ₂ O, there was no attack on the diamond surface, but the etching rate was as small as 0.96 μm / h.
Incidentally, when to flow the Air instead of N 2 _{+ H} 2 _O mixed gas, although observed approximately etching rate 15 [mu] m / h, the diamond surface of a portion Ni film is not formed was also etched.
This proved that H ₂ O in the N ₂ + N ₂ O mixed gas attacked the diamond surface via the Ni film.

<Experiment 2>
Next, as shown in FIG. 4, an Ni pattern was formed on the surface of the diamond substrate having a (110) crystal plane by changing the angle as shown in FIG.
At this time, the Ni film degree was about 500 nm.
This diamond substrate was placed in an electric furnace and annealed (etched) under the same conditions as in Experiment 1.
Then, the 0 ° Ni pattern is shown in FIGS. 5 (c) and 5 (d) in a schematic diagram, the etched shape as shown in FIG. 6 is shown in the photograph, and the 45 ° Ni pattern is a schematic diagram in FIG. (F) The etched shape as shown in the photograph and FIG. 7 was obtained.
Here, the etching side is confirmed to be stopped by the crystal orientation {111} plane, the angle theta ₂ shown in FIG. 6 was 35.2 °.

<Experiment 3>
Etching was performed under the same conditions as in Experiment 1 except that the atmosphere temperature of the electric furnace was set to 1000 ° C.
As a result, a through hole was formed in the diamond substrate of about 0.3 mm in 5 minutes, and it was confirmed that the etching rate was further increased.

The above experiment was an example in which a Ni film was formed on the surface of diamond, but subsequent confirmation confirmed the same etching process with an Fe film, an oxide film of Si, and an oxide film of Al.
<Industrial applicability>

  INDUSTRIAL APPLICABILITY The diamond etching method according to the present invention can be used for various processing of diamond, such as production of various devices in the field of electronics and a method of cutting bulk diamond.

Claims (1)

Forming a film of any of a Ni film, a Fe film, an oxide film of Si, and an oxide film of Al on the diamond processing portion, and then, when H ₂ O is in the range of 0.01 to 30%. A step of performing anisotropic etching along a predetermined crystal plane of the diamond at a portion where the film is formed using a mixed gas containing an inert gas ,
Wherein by etching temperature is 500 ° C. or higher, the processing method of diamond which comprises carrying out a melt temperature below ambient temperature of the film.