CH4/N2 Plasma Etching for Organic Low-k Dielectric Material

Abstract

The etching of an organic low-dielectric-constant (low-k) material, FLARE, with gas mixtures of CH4/N2 and H2/N2 was investigated in a magnetic neutral loop discharge (NLD) plasma system. The hole-etching profile of FLARE with a SiO2 hard mask and reactive ion etching (RIE) lag characteristics (the etch rate depends on the hole size) were studied for hole diameters from 0.16 to 0.4 µm. We discuss the role of CH4 in organic low-k etching and consider the etching mechanism in a CH4/N2 plasma in comparison with that in a H2/N2 plasma. Etching with no RIE lag was achieved at a CH4 concentration of about 30% with a total flow of 100 sccm, pressure of 0.4 Pa, source power of 1000 W, and bias power of 200 W in a CH4/N2 plasma. FLARE etching profiles with a perpendicular or normal taper and no microtrenching were obtained with CH4 concentrations below about 70%. We used X-ray photoelectron spectroscopy (XPS) to evaluate films deposited on a Si substrate during etching under several plasma conditions to clarify the mechanism of the organic low-k material etching.