Plasma Induced Subsurface Reactions for Anisotropic Etching of Organic Low Dielectric Film Employing N2and H2Gas Chemistry

Subsurface reactions of organic low dielectric (low k ) film exposed to plasmas with low ion bombardment energy were investigated by a real time analysis of Fourier transform infrared attenuated total reflection (FT-IR ATR). The exposure of N 2 plasma resulted in the formation of a CN layer composed of C(sp 2 )=N and C(sp 3 )–N bonds. After the N 2 plasma exposure, the surface was exposed to H 2 plasma. C(sp 1 )≡N and C(sp 2 )=N bonds were removed by the H radicals, while the C(sp 3 )–N bond remained. It was found that the C(sp 3 )–N bond was the key chemical bond against H 2 plasma exposure. Based on the analyses, a reaction model for anisotropic profile in organic low k film etching employing N–H plasmas is proposed.