Low-k materials etching for FLARE (TM) and a porous silica were carried out in a magnetic neutral loop discharge plasma at low pressure, below 1 Pa. Fluorinated carbon molecules were used as etching gases for porous silica. The etch rate of the porous silica was approximately two times higher than that of thermal SiO2 This result means that consumption of perfluoro compound (PFC) gases is suppressed below at approximately half volumes. And organic low-k materials etching where ammonia gas or a gas mixture of nitrogen and hydrogen were used instead of PFC gas is an environmentally friendly process. After investigating an influence of a N-2/H-2 mixture ratio in the organic materials etch process, a good experimental condition to get a low microloading profile was found at a N-2 ratio of 70%-80%. Under this condition N-2(+) and N2H+ ions were dominant, and the signal intensity of the N2H+ ion showed a maximum value in the mass spectrum. This may mean N-2(+) and N2H+ ions play an important role for a low microloading etching. The nitrogen may be 2 adsorbed on the surface and a thin passivation film may be created on the sidewall surface.