Effect of sputtering with hydrogen dilution on fluorine concentration of low hydrogen content fluorinated amorphous carbon thin films with low dielectric constant

The fluorine concentration of fluorinated amorphous carbon $\mathrm{(a-}\mathrm{C:F})$ thin films with a low dielectric constant was controlled using magnetron sputtering with hydrogen gas dilution into ${\mathrm{CF}}_{\mathrm{4}}$ gas. The structural, optical and defect properties of these films were investigated by infrared (IR) absorption, x-ray photoelectron spectroscopy, ultraviolet visual spectroscopy and electron spin resonance as well as dielectric constant measurements. IR absorption spectra of the films with various fluorine concentrations prepared by hydrogen gas dilution showed no vibration modes between hydrogen and carbon atoms in CH, ${\mathrm{CH}}_{\mathrm{2}},$ and ${\mathrm{CH}}_{\mathrm{3}}$ configurations, suggesting that the hydrogen concentration of these films is less than a few at. %. Furthermore, the structural properties change at a fluorine concentration of approximately 50 at. %. However, the dielectric constant of 2.5 that is required for the interlayer materials for the next generation of ultralarge scale integrated devices remains unchanged at this fluorine concentration. Based on these results, the thermal stability of these $\mathrm{a-}\mathrm{C:F}$ films is discussed briefly.