Dry etching properties of methyl-BCN film with C4F8 gas for Cu/low-k interconnection

Methyl-BCN is an attractive low-k material for the fabrication of next generation LSI device system. This paper describes dry etching of methyl-BCN film in order to develop interconnections for future devices. The methyl-BCN films were deposited by plasma-assisted chemical-vapor deposition (PACVD) using tris(dimethylamino)boron (TMAB) gas at 350 °C. We have investigated dry etching properties and mechanism of the methyl-BCN film using C₄F₈ gas with induced coupling plasma (ICP) etching equipment. In this study we used C₄F₈ gas whose atmospheric lifetime is less than one-sixteenth of the conventional CF₄ gas for suppression greenhouse gases. It was found that methyl bonds in the methyl-BCN film can be kept after dry etching, because the peak of C–H (2962 cm^?1) in Fourier transform infrared absorption (FTIR) spectra didn't significantly change after dry etching. X-ray photoelectron spectroscopy (XPS) analysis shows the presence of C–F₂ and C–F₃ bonds just on the methyl-BCN surface after dry etching and no traces of these bonds inside the film. It is observed that intensities of B–N and B–C bonds decrease after dry etching. This suggests that the etching of methyl-BCN films by C₄F₈ gas mainly involves boron desorption.