Plasma-assisted chemical gas separation method having increased plasma density and device for implementing the method
The invention relates to a method and a device for coating surfaces of a substrate ( 8 ) according to the technique of plasma-assisted chemical vapor deposition. The basic idea of the present invention is to increase the ion concentration prevailing in the plasma so as to have more ions accumulate on the substrate ( 8 ) and to promote layer growth ( 12 ). According to the invention, the ion concentration is increased by forming a so-called fireball at the surface of the substrate ( 8 ) to be coated. The term fireball refers to the ionization processes that occur on electrode surfaces ( 2 ) as spontaneous small brightly luminescent phenomena in plasma processes. To this end, an electrode ( 2 ) is introduced into an existing background plasma and connected to a positive potential ( 4 ).
1. A method for coating surfaces of a substrate according to the technique of plasma-assisted chemical vapor deposition, comprising increasing the plasma density of an existing background plasma at the surface of the substrate ( 8 ) by forming a fireball ( 6 ) at a positively biased ( 4 ) electrode surface ( 2 ), wherein the fireball ( 6 ) is excited as an inverted fireball ( 6 ), which forms in an interior of a cavity-forming grid electrode ( 2 ) and wherein the supply of energy per unit of time into the existing background plasma is reduced once the fireball ( 6 ) has formed.
2. The method according to claim 1 , characterized in that an electrical bias is applied to the substrate ( 8 ).
3. The method according to claim 1 , characterized in that the existing background plasma is excited by laser radiation.
4. The method according to claim 1 , characterized in that the existing background plasma is excited by supplying electrical and/or magnetic energy.
5. The method according to claim 1 , characterized in that a diamond layer is deposited from methane and hydrogen.
6. The method according to claim 1 , characterized in that an organic boron compound is added to the reaction gas and thus a boron-doped diamond layer is deposited.
7. The method according to claim 1 , characterized in that one of the following deposition processes takes place:
a silicon nitride layer is deposited from ammonia and di-chlorosilane,
a silicon oxide layer is deposited from silane and oxygen or tetraethyl orthosilicate,
a silicon/metal compound is deposited from tungsten hexafluoride,
a silicon carbide layer is deposited from hydrogen and methyl-trichlorosilane,
titanium nitride is deposited from tetrakis(dimethylamino)titanium 1 (TDMAT) and nitrogen,
silicides are deposited from organic compounds,
tin oxide layers are coated onto glass from tin chloride or organotin compounds by means of water vapor or oxygen,
boron carbide is deposited.
8. A device for coating surfaces of a substrate ( 8 ) according to the technique of plasma-assisted chemical vapor deposition method of claim 1 , comprising an electrode surface ( 2 ) for forming the inverted fireball ( 6 ), said electrode surface being arranged in a reaction chamber and being positively biased ( 4 ) and being designed as a cavity forming grid electrode ( 2 ), the inverted fireball forming in its interior.