Effect of etching on dielectric constant and surface composition of SiCOH low-k films in inductively coupled fluorocarbon plasmas

摘要

SiCOH low-k (k = 2.8) film etched in fluorocarbon (CF_4 and CHF_3) inductively coupled plasmas was characterized in this work. The surface composition and molecular structures of the low-k films after etching in the CF_4, CHF_3, CF_4/Ar, and CHF_3/Ar plasmas were characterized. A higher etch rate was observed with the CF_4 plasmas than with the CHF_3 plasmas. The etch rate of the low-k film in the CF_4 plasmas was decreased and the etch rate in the CHF_3 plasmas was increased by the Ar addition. After etching the low-k films, a decrease in the dielectric constant of up to 0.19 was observed. The thickness of the fluorocarbon (CF_x) layer and CF_x (x = 1,2,3)-to-carbon ratio obtained from the XPS C 1s peak increased with decreasing etch rate. The k-value was correlated with amount of Si-CH_3 and Si-0 related groups determined from the Fourier transform infrared (FT-1R) spectrum. The Si-0 related peaks were markedly decreased after etching in the CF_4 and CF_4/Ar plasmas. The lower k-value was attributed to the increase of the Si-CH_3/Si-O ratio after etching low-k film.