Process and apparatus for chemical vapor deposition of diamond films using water-based plasma discharges
Rudder, R., Hudson, G., Hendry, R., Markunas, R., & Mantini, M. (1996). IPC No. U.S.Process and apparatus for chemical vapor deposition of diamond films using water-based plasma discharges (Patent No. 5480686.)
A chemical vapor deposition (CVD) process and apparatus for thegrowth of diamond films using vapor mixtures of selected compoundshaving desired moieties, specifically precursors that providecarbon and etchant species that remove graphite. The processinvolves two steps. In the first step, feedstock gas enters aconversion zone. In the second step, by-products from theconversion zone proceed to an atomization zone where diamond isproduced. In a preferred embodiment a feedstock gas phase mixtureincluding at least 20% water which provides the etchant species isreacted with an alcohol which provides the requisite carbonprecursor at low temperature (55.degree.-1100.degree. C.) and lowpressure (0.1 to 100 Torr), preferably in the presence of anorganic acid (acetic acid) which contributes etchant speciesreactant. In the reaction process, the feedstock gas mixture isconverted to H.sub.2, CO, C.sub.2 H.sub.2, no O.sub.2, with someresidual water. Oxygen formerly on the water is transferred to CO.Hence, an etchant species (H.sub.2 O, OH, O) is replaced in thereactor by CO, a growth species and prevents undesirous consumptionof diamond (the net-product). In a preferred embodiment, theapparatus assures conversion by preventing gas circumvention of theconversion zone prior to dissociation in the hydrogen atomizationzone to produce the necessary atomic hydrogen for diamondgrowth.