Effect of Cu Diffusion on Electrical and Reliability Characteristics of Low Dielectric Constant Dielectrics

Abstract

The interaction between copper (Cu) interconnect and dense or porous low dielectric constant films (low-k) under thermal annealing was investigated in this study. A fabricated Metal-Oxide-Semiconductor (MOS; Cu/low-k/Si) capacitor was used to study the electrical and reliability characteristics of low-k films under Cu diffusion. The experimental results show that Cu diffusion depth increased with the annealing temperature and annealing time in both dense and porous low-k films. Moreover, the Cu diffusion rate in the porous low-k films is faster and is dominated by the annealing temperature, so that a large increase in the electrical properties was observed. Furthermore, the increase in the dielectric constant and the dielectric breakdown failure time were found to be proportional to the Cu diffusion depth for both dense and porous low-k films. Therefore, the Cu diffusion depth can be an indication for the fast reliability evaluation in the future Cu/low-k interconnects applications.