Effect of Bias-Voltage in H2/N2 Plasma Treatment on Porous Low Dielectric Constant Materials

Porous low-dielectric constant (low-k) materials are needed for advanced technologies to improve signal propagation. Plasma treatments in interconnection fabrication have been considered to be critical steps to impact the low-k films’ properties. In this study, the degradation of the porous low-k films by plasma exposure using several kinds of treatment conditions was investigated in this study. The increase of the dielectric constant and the degradation of the porous low-k film reliability were found to be related to the decreased amount of Si-CH₃ bonds and the absorbed amount of H₂O or OH groups in the film. Pure H₂ gas plasma treatment extracts more CH₃ group from the porous low-k film and forms a larger amount of H₂O or OH groups. Although N₂ gas plasma treatment can suppress H₂O or OH group formation, the increase of the dielectric constant is higher due to the formation of Si-N or C-N bonds. The plasma treatment using a mixture gas of H₂ and N₂ can obtain a balance result in the dielectric constant increase and absorbed moisture uptake. Furthermore, introducing an increasing bias-voltage on the sample electrode during H₂/N₂ Plasma treatment can effectively suppress the degradation of the porous low-k films.