Stock material or miscellaneous articles – Self-sustaining carbon mass or layer with impregnant or...
Reexamination Certificate
1997-12-22
2001-03-27
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Self-sustaining carbon mass or layer with impregnant or...
C257S077000, C428S141000, C428S156000, C428S446000
Reexamination Certificate
active
06207282
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method of smoothing the surface of substrates such as diamonds which are applied for industrial purposes. More specifically, this invention relates to a surface treatment method for smoothing and etching the surface of diamonds which are useful as electronic devices, of diamond films formed by the CVD (chemical vapor deposition) method.
BACKGROUND OF THE INVENTION
Since diamond has high hardness and a wide band gap, the application of diamond is being tested as a coating material for a device, a light transmitting material, a high frequency semiconductor, an electronic device capable of operating at high temperature, or the like. As a method of artificially forming diamond, the CVD method applicable to various substrate materials is mainly used. In the CVD method source, gas including carbon atoms is dissociated and reacted at low pressure, thus forming a diamond film on a substrate surface. Generally known CVD diamond films are in a polycrystalline state, and have unevenness on the growth surface. Thus, in order to apply a CVD polycrystalline diamond film formed on a large area of a substrate to various purposes, the diamond film should be smoothed. In addition to the smoothing of a diamond surface, an etching technique of to form preferable patterns is also required.
Conventional smoothing methods of a diamond surface are a mechanical polishing treatment, the method of etching the surface with laser irradiation in an oxygen atmosphere, a reactive ion etching (RIE) method with etching gas such as argon and oxygen, a physical etching with single ion irradiation (“Diamond No Ion Beam Kako” (Ion Beam Smoothing of Diamonds), New Diamond, Vol.5, No.1, 18-25(1989)), and the like.
However, generally speaking, diamonds are extremely hard and stable chemically, so that it is difficult to smooth diamonds by conventional mechanical polishing treatments and etching methods. Moreover, in the conventional methods, the processing efficiency and the precision are poor.
SUMMARY OF THE INVENTION
It is an object of this invention to solve the above-mentioned conventional problems by providing a method for efficiently smoothing and etching the surface of diamond films having unevenness.
In order to accomplish this objective, the substrate surface treatment method of this invention includes the steps of forming culster particles constituted by a plurality of atoms or molecules, of accelerating the cluster particles, and of irradiating the accelerated cluster particles onto the surface of a substrate in a reduced pressure atmosphere.
It is preferable that the accelerated cluster particles are prepared by forming cluster particles formed of a plurality of atoms or molecules, by selecting cluster particles having a specified mass, and by accelerating selected cluster particles having the specified mass.
It is also preferable that the substrate is a diamond.
It is preferable that the number of atoms or molecules constituting the cluster particle is from two to 10,000.
It is further preferable that the number of the atoms or the molecules constituting the cluster particle is from 100 to 5,000.
It is also preferable that the cluster particle is in a cluster ion.
It is further preferable that the cluster particles have the same mass.
It is preferable that molecules constituting the cluster particle are inert gas molecules.
It is preferable that the molecules constituting the cluster particle are argon (Ar) molecules.
It is also preferable that the molecules or atoms constituting the cluster particle include at least oxygen as a constituent element.
It is preferable that the molecules constituting the cluster particle are carbon dioxide (CO
2
) molecules.
It is also preferable that the molecules constituting the cluster particle are oxygen (O
2
) molecules.
It is further preferable that the accelerated cluster particle has an energy of 200 keV or less.
It is preferable that the substrate is kept below 650° C. when the accelerated cluster particles are irradiated onto the substrate.
It is preferable that the cluster particles are irradiated onto the substrate in a reduced pressure atmosphere including a gas which contains oxygen.
It is also preferable that the surface of the substrate is smoothed so as to flatten surface features exceeding 100 nm to less than 100 nm.
The substrate surface of the first aspect of the invention includes a product prepared by the process of a substrate surface treatment method comprising the steps of: forming cluster particles comprising a plurality of atoms or molecules; accelerating the cluster particles; and irradiating accelerated cluster particles onto a surface of a substrate in a reduced pressure atmosphere.
It is preferable that the diamond on a surface thereof which has been irradiated with the accelerated cluster particles.
It is preferable that the substrate and a diamond coating on a surface of the substrate.
It is preferable that the substrate is silicon.
It is preferable that the substrate is a single crystal diamond substrate.
The substrate surface of the second aspect of the invention includes a product having a diamond surface, whrerin the diamond surface has a surface roughness of no more than about 10 nm.
It is preferable that the substrate and a diamond coating on a surface of the substrate.
It is preferable that the substrate is silicon.
It is preferable that the substrate is a single crystal diamond substrate.
It is preferable that the electronic device comprising the product of the first aspect of the invention.
It is preferable that the product of the second aspect of the invention.
It is preferable that the light transmitting material comprising the product of the first aspect of the invention.
It is preferable that the product of the second aspect of the invention.
It is preferable that the product of the first aspect of the invention.
It is preferable that the product of the second aspect of the invention.
The surface of diamond films having unevenness is efficiently smoothed by the surface treatment method of the invention of forming cluster particles constituted by a plurality of atoms or molecules, accelerating the cluster particles, and irradiating the accelerated cluster particles onto a substrate in a reduced pressure atmosphere.
When particles having a certain energy are irradiated onto a material, the surface of the material is physically etched by a sputtering. Thus, polycrystalline diamond layers are smoothed by etching the uneven surfaces of the layers with the irradiation of accelerated particles. However, when particles such as single ions are irradiated so as to etch a polycrystalline diamond, the ions are injected into the diamond or give damage to the diamond. Especially due to the damage, the diamond is likely to become graphite, and it is difficult to remove the damage. Moreover, since the ions having energy are highly directional, it is difficult to reduce the only surface roughness of the diamond. Thus, the irradiation of single particles is not suitable for smoothing a diamond.
On the other hand, when cluster particles constituted by a plurality of particles (molecules or atoms) having the same energy as single particles are irradiated onto a diamond, each particle in the cluster has equivalently low energy. As a result, damade to the diamond is prevented without reducing etching properties. In addition, a multi-body collision effect is generated by interaction between the cluster particles and a diamond, thus increasing spattering efficiency and etching rate. The cluster particles collide against a diamond and break apart into individual molecules or atoms, and the molecules or atoms scatter while changing their momentum (direction and speed) and energy. Therefore, the sputtering effect in a lateral direction becomes notable, and the surface roughness of the diamond are reduced selectively a nd smoothed by the irradiation of the accelerated cluster particles onto the polycrystalline diamond.
The cluster particles having a specified mass are selected and irradiated onto a diamo
Deguchi Masahiro
Hirao Takashi
Kitabatake Makoto
Yoshida Akihisa
Matsushita Electric - Industrial Co., Ltd.
Merchant & Gould P.C.
Turner Archene
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