Ca. Rego et al., GAS-PHASE COMPOSITION MEASUREMENTS DURING CHLORINE ASSISTED CHEMICAL-VAPOR-DEPOSITION OF DIAMOND - A MOLECULAR-BEAM MASS-SPECTROMETRIC STUDY, Journal of applied physics, 79(9), 1996, pp. 7264-7273
We have constructed a molecular beam mass spectrometer designed specif
ically to sample gases from a diamond chemical vapor deposition (CVD)
process chamber thereby enabling characterization of the gas-phase CVD
environment. With this in situ diagnostic technique we have obtained
quantitative measurements of the composition of the gas-phase species
as a function of filament temperature for a variety of C/H/Cl gas mixt
ures. The precursor mixtures used were 1% of a chloromethane (CH4-nCln
, n=1-4) in hydrogen and 1% CH4 in hydrogen with added Cl-2 varying fr
om 1% to 4%. At filament temperatures optimum for diamond growth (simi
lar to 2300 degrees C) the relative CH4/C2H2/C2H4 product distribution
measured in the gas mixture is remarkably similar to that established
when CH4 is the carbon precursor species. At these filament temperatu
res almost all the chlorine is reduced to HCl, its concentration being
proportional to the Cl fraction in the source gas, regardless of the
form of the chlorine in the source gas mixture. Compositional analysis
of the as-grown diamond films indicated that no chlorine was present
in the bulk of the films, though trace amounts of chlorine were detect
ed on the film surface. From these observations we surmise that chlori
ne atoms are involved in the gas-surface reactions which produce activ
e growth th sites on the diamond surface. (C) 1996 American Institute
of Physics.