DEPENDENCE OF CF2 CONCENTRATION ON PRECURSOR IN THE GEC RF PLASMA REACTOR
USING PLANAR LASER-INDUCED FLUORESCENCE. Kristen L. Steffens and Michael
R. Zachariah, Building 221, Room B318, National Institute of Standards and
Technology, Gaithersburg, Maryland, USA (301-975-2656, email:firstname.lastname@example.org)
Low-pressure radio-frequency (rf) plasmas are extensively used during microelectronics device fabrication. To better understand the chemistry of these plasmas, models are under development. Spatially-resolved two-dimensional measurements of the species concentrations in the plasmas, measured in the standardized parallel-plate Gaseous Electronics Conference (GEC) reference cell, provide necessary input and verification for these plasma models. Planar laser-induced fluorescence (PLIF) is a sensitive non-intrusive technique of determining the two-dimensional relative density map of various free-radical intermediates which are crucial to plasma chemistry. PLIF eliminates the need for multiple point measurements. Here, PLIF is used to map out the spatially-resolved two-dimensional relative concentration of CF2 in low-pressure hydrofluorocarbon/Ar rf plasmas generated in a 13.56 MHz, parallel-plate GEC reference cell. Also, two-dimensional light scattering has been used to determine where particles are trapped in the plasmas. To investigate the effect of precursor chemical structure versus precursor elemental ratio on CF2 two-dimensional relative density and particle generation and trapping, two series of experiments are performed. First, elemental composition of the fluorocarbon precursor is varied. Next, the elemental ratio C:F:H is kept constant by using various mixtures of CHXFY/Ar. It was found that elemental composition has a large effect on CF2 density and on particulate formation and trapping. With constant elemental composition, the precursor chemical structure has little effect on CF2 density, but greatly effects particle generation and trapping.