Ion and substrate effects on surface reactions of CF2 using C2F6, C2F6/H2, and hexafluoropropylene oxide plasmas

The surface reactivity of CF2 radicals has been characterized during plasma processing of a variety of substrates using the imaging of radicals interacting with surfaces technique. The plasma molecular beam sources are 100% C2F6, 50/50 C2F6/H2, and 100% hexafluoropropylene oxide (HFPO) gas mixtures. Simulation of spatially resolved laser-induced fluorescence images in the 100% C2F6 system shows that CF2 has a scatter value, S, >1.0 with SiO2, polyimide and photoresist substrates. A scatter of >1.0 indicates that CF2 molecules are generated at the surface during plasma processing. With the 50/50 C2F6/H2 plasma, CF2 exhibits a lower scatter value (∼0.85) on Si, SiO2, and polyimide substrates. With the HFPO plasma source, S⩾1 for all continuous wave powers and substrates processed. Values of S∼0.8 are obtained for ion-free and pulsed plasmas, however, revealing ion collisions with the substrate play an important role in the surface generation of CF2. The radical-surface interaction data are correlated with data from surface characterization by x-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy of the substrates. The key finding is that our results suggest the surface reactivity behavior of CF2 radicals correlates well to the overall plasma process (etching or deposition).