Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Reexamination Certificate
2001-11-29
2004-03-23
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
C428S408000, C428S174000
Reexamination Certificate
active
06709730
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of making a diamond product by etching, and the diamond product.
2. Related Background Art
Plasma etching, which can remove a large amount of diamond at once and can be carried out relatively easily, has been utilized as a technique for processing diamond. Usually, oxygen gas is used for plasma etching of diamond. Etching with oxygen alone, however, has formed a large number of unnecessary acicular protrusions on the surface of the resulting diamond product, thus failing to smooth the surface. Therefore, attention has been given to a technique in which other gases are introduced into a reaction chamber together with oxygen gas so as to flatten the diamond surface. For example, Hiroshi Shiomi,
New Diamond,
Vol. 13, No. 4, p. 28 (1997) discloses a technique in which diamond is etched with a plasma of a mixed gas composed of oxygen gas and CF
4
gas. This etching technique enables the plasma of CF
4
gas to remove the unnecessary acicular protrusions and flatten the surface of diamond product.
SUMMARY OF THE INVENTION
However, the technique disclosed in the above-mentioned publication has the following problem. Namely, when a diamond substrate
102
is etched by way of a mask
104
as shown in
FIG. 14A
, thus etched side faces
102
S may not become perpendicular but tilt greatly as shown in
FIG. 14B
, thus yielding a trapezoidal cross section.
In order to overcome the above-mentioned problem, it is an object of the present invention to provide a method of making a diamond product, which can fully flatten the surface of diamond product and make its etched side faces substantially perpendicular; and such a diamond product.
The inventors carried out diligent studies and, as a result, have found that the above-mentioned object can be achieved by the following invention.
Namely, the present invention provides a method of making a diamond product by etching, the method comprising the steps of forming a diamond substrate with a mask layer; and etching the diamond substrate formed with the mask layer with a plasma of a mixed gas composed of a gas containing an oxygen atom and a gas containing a fluorine atom; wherein the fluorine atom has a concentration within the range of 0.04% to 6% with respect to the total number of atoms in the mixed gas.
The inventors have found that, though the unnecessary protrusions can be eliminated when the fluorine concentration in the etching gas is raised, the mask layer is laterally shaved with fluorine when its concentration is too high, so that the etched side faces may incline. In recognition of this fact, the inventors have found that, when the fluorine atom concentration is lowered so as to fall within the above-mentioned range, the mask layer is restrained from being shaved laterally, whereby the etched side faces can be made substantially perpendicular; and that, even when the fluorine atom concentration is lowered so as to fall within the above-mentioned range, the number of unnecessary protrusions is sufficiently reduced, whereby the etched surface of diamond product is flattened.
Preferably, in the method of making a diamond product in accordance with the present invention, the plasma is produced by generating a high-frequency discharge between two plate electrodes arranged in parallel, whereas the high-frequency discharge is generated by supplying an electric power of at least 0.45 W/cm
2
between the plate electrodes.
When the output for generating the high-frequency discharge is enhanced as such, it becomes easier for the fluorine atom to attain a plasma state, whereby the number of unnecessary protrusions can sufficiently be reduced even when the amount of fluorine is small.
Preferably, in the method of making a diamond product in accordance with the present invention, the gas containing the fluorine atom is CF
4
gas, whereas the CF
4
gas has a concentration within the range of 0.02% to 3% with respect to the total number of molecules in the mixed gas.
When CF
4
gas, which is safe and easy to use, is employed, an etching process for the diamond substrate can be carried out smoothly.
Preferably, in the method of making a diamond product in accordance with the present invention, the gas containing the oxygen atom is one of O
2
, CO
2
, and a mixed gas composed of O
2
and CO
2
.
The diamond product in accordance with one aspect of the present invention comprises a diamond substrate; a plurality of aligned protrusions made of diamond, formed on the diamond substrate by etching, and arranged according to a predetermined rule; and a plurality of subsidiary protrusions randomly formed between the plurality of aligned protrusions upon etching; wherein the aligned protrusions have a side face with an angle of inclination of at least 78°, whereas the subsidiary protrusions have a top part which is not flat, and the number of the subsidiary protrusions is not greater than 20 per 25 &mgr;m
2
.
Among diamond products in which a plurality of protrusions are formed by etching, those having such a small number of subsidiary protrusions with their aligned protrusions having side faces with an angle of inclination of at least 78° have not conventionally existed. For example, the above-mentioned manufacturing method of the present invention can make a diamond product having a flat surface with aligned protrusions having substantially perpendicular side faces as such. The portion of diamond substrate covered with the mask layer can attain a flat top part when the mask layer is removed. However, the subsidiary protrusions are formed in a portion not covered with the mask, whereby their top part is not flat. Here, the condition that the number of the subsidiary protrusions is not greater than 20 per 25 &mgr;m
2
also encompasses the case where there is no subsidiary protrusion.
The diamond product in accordance with another aspect of the present invention comprises a diamond substrate having a recess formed by etching; and a plurality of subsidiary protrusions randomly formed at a bottom part of the recess upon etching; wherein the recess has a side face with an angle of inclination of at least 78°, whereas the subsidiary protrusions have a top part which is not flat, and the number of the subsidiary protrusions is not greater than 20 per 25 &mgr;m
2
.
Among diamond products in which a recess is formed by etching, those having such a small number of subsidiary protrusions with their recess having a side face with an angle of inclination of at least 78° have not conventionally existed. The above-mentioned manufacturing method of the present invention can make a diamond product having a flat surface (bottom part of the recess) with the recess having a substantially perpendicular side face as such. Here, the condition that the number of the subsidiary protrusions is not greater than 20 per 25 &mgr;m
2
also encompasses the case where there is no subsidiary protrusion.
The diamond product in accordance with another aspect of the present invention comprises a diamond substrate; one protrusion made of diamond and formed on the diamond substrate by etching; and a plurality of subsidiary protrusions randomly formed about the one protrusion upon etching; wherein the one protrusion has a side face with an angle of inclination of at least 78°, whereas the subsidiary protrusions have a top part which is not flat, and the number of the subsidiary protrusions is not greater than 20 per 25 &mgr;m
2
.
Among diamond products in which one protrusion is formed by etching, those having such a small number of subsidiary protrusions with the one protrusion having a side face with an angle of inclination of at least 78° have not conventionally existed. The above-mentioned manufacturing method of the present invention can make a diamond product having a flat surface with the one protrusion having substantially perpendicular side faces as such. The portion of diamond substrate covered with the mask layer can attain a flat top part when the mask layer is removed. However, the subsidiar
Ando Yutaka
Imai Takahiro
Meguro Kiichi
Nishibayashi Yoshiki
McDermott & Will & Emery
Sumitomo Electric Industries Ltd.
Turner Archene
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