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CFX (X=1–3) radicals were found to be generated from fluorocarbon films deposited on the reactor wall when the films are irradiated with plasmas. In this process, the fluorocarbon films were first formed on the reactor wall by electron cyclotron resonance (ECR) etching plasmas employing C4F8 and C4F8/H2 gases, and subsequently irradiated with an ECR-Ar plasma. CFX radical densities were measured during the Ar plasma by infrared diode laser absorption spectroscopy. CF3 radical density in the Ar plasma was estimated to be the same order as that in the C4F8 plasma. the fluorocarbon films deposited on the reactor wall were investigated by x-ray photoelectron spectroscopy. These results will offer valuable information for the production mechanism of CFX radicals in the etching process employing fluorocarbon gases.

Temporal variations in densities of CF and CF2 radicals were measured at rising phases of plasma ignition in CF4 and C4F8 electron-cyclotron-resonance (ECR) plasmas by infrared diode laser absorption spectroscopy. It was found that CF2 radical densities at the rising phase briefly became larger than those at the steady state in the C4F8 plasma. This finding shows that the CF2 is generated in abundance by the rapid dissociation of C4F8 molecules at the discharge ignition. The variations of CF2 and CF radical densities were demonstrated using a computer calculation to characterize the chemistry in the CF4 and C4F8 plasmas numerically. Chemical models in the CF4 and C4F8 ECR plasmas were presented based on the results obtained by the experiment and calculation. The models suggested that the higher fluorocarbons, that is CXFY (X ≥2), were important in the C4F8 plasma as dissociation paths from C4F8 molecules to CFX (X=1–3) radicals and as polymer precursors.

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