Precursors of fluorocarbon film growth studied by mass spectrometry

The precursor species of fluorocarbon film growth at the reactor wall irrad iated by an electron cyclotron resonance C4F8 plasma have been studied by u sing a quadrupole mass spectrometer. The amount of polymeric neutral specie s [CmFn (m greater than or equal to 2)] and absolute densities of CFx (x = 1-3) radicals in the vicinity of the wall were measured by electron attachm ent and threshold ionization mass spectrometry, respectively. The trends in the film growth rate as a function of gas residence time, diluted hydrogen concentration, and microwave power were well accounted for by the competit ion between the incorporation of CFx radicals and positive ions and the rem oval by F and H atoms. The fluxes of CFx radicals and positive ions inciden t upon the wall were shown to be comparable with the net condensed carbon f lux derived from the growth rate. In contrast, the trends in the amount of polymeric neutrals were not well correlated to the growth rate. (C) 2000 Am erican Institute of Physics. [S0021-8979(00)01810-7].