Dry etching properties of methyl-BCN film with C_4F_8 gas for Cu/low-k interconnection

摘要

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 C_4F_8 gas with induced coupling plasma (ICP) etching equipment. In this study we used C_4F_8 gas whose atmospheric lifetime is less than one-sixteenth of the conventional CF_4 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-F_2 and C-F_3 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 C_4F_8 gas mainly involves boron desorption.