Mass spectrometric investigation and formation mechanisms of high-mass species in the downstream region of Ar/CF(4)/O(2) plasmas.

Mass analysis has been conducted on the positive ions and neutral species in the downstream region of Ar/CF(4)/O(2) plasmas. The neutral species have been ionized by Li(+) attachment before mass analysis. The CF(2)O(+), C(2)F(5)O(+) and C(n)F(2n-1)O(+) (1 or= 4) have been observed as the species composed only of C and F. These findings suggest that C(n)F(2n)O (n>or= 3) are produced mainly through the following reactions: CF(3)(CF(2))(m)CF = CF(2) + O((3)P) --> CF(2)((3)B(1)) + CF(3)(CF(2))(m)CFO (m>or= 1) and CF(3)(CF(2))(m)CF = CF(CF(2))(n)CF(3) + O((3)P) --> CF(3)(CF(2))(m)CF + CF(3)(CF(2))(n)CFO (m, n>or= 1), where the CF(3)(CF(2))(n)- group might have side chains, as in (CF(3))(2)CF(CF(2))(n-2)-. With the help of quantum chemistry calculations of reaction enthalpies and transition states, the formation mechanisms of the observed species have been discussed in detail.