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

Abstract

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. This study investigates the degradation of the porous low-k films by plasma exposure using several kinds of treatment conditions. Experimental results indicate that the increase in the dielectric constant and the degradation in the reliability for the plasma-treated low-k films were related to the decreased amount of Si-CH3 bonds and the absorbed amount of H2O or OH groups within the film. Plasma treatment with pure H2 gas extracts more CH3 groups from the porous low-k film and forms a larger amount of H2O or OH groups. Although the plasma-treated low-k films using N2 gas can suppress H2O or OH group formation, the increase in the dielectric constant is higher due to the formation of Si-N or C-N bonds. Plasma treatment using a mixture of H2/N2 gas can obtain a balance result in the dielectric constant increase and absorbed moisture uptake. Furthermore, increasing bias-voltage on the sample electrode during H2/N2 Plasma treatment can effectively suppress the degradation of the porous low-k dielectrics.