Plasma processes of interest to the growth of ultrananocrystalline diamond and to etching of silicon semiconductors

D. M. Gruen

Argonne National Laboratory, 9700 S. Cass Avenue, Materials Science Division, Argonne, IL 60439 USA

Plasma processes and plasma chemistries determine the fact that argon microwave discharges containing small amounts of CH₄ lead to the growth of ultrananocrystalline diamond (UNCD) films, but if the carbon containing molecule is CF₄, etching of silicon semiconductors occurs instead. For UNCD synthesis, the growth species is carbon dimer, C₂, while etching occurs largely as a result of reactions of fluorine atoms, F, with silicon to form SiF₄. The details of the production processes of these reactive species are still being elucidated. It is clearly important to achieve a sound fundamental understanding of mechanisms so as to be able to optimize growth rates of diamond on the one hand and etch rates of silicon, on the other.

It turns out that important initial processes for the creation of both C2 and F are charge-transfer (CT) and Penning ionization of Ar⁺ and Ar^* respectively with hydrocarbons in the case of diamond and with halocarbons in the case of silicon etching. Thermal energy CT and Penning ionization reactions of noble gas ions with simple molecules of interest will be discussed. A scheme will be proposed for the efficient production of C₂ both from C₆₀ and from CH₄ making use of dissociative electron recombination reactions.

Characterization, properties and applications of UNCD films will be briefly reviewed.

Work supported by the U.S. Department of Energy, BES-Materials Sciences, under Contract W-31-109-ENG-38.