Ultrathin (5-35 nm) SiCNH Dielectrics for Damascene Cu Cap Application: Thickness Scaling and Oxidation Barrier Performance Limitation

The scaling limit of plasma enhanced chemical vapor deposited (PECVD) ultrathin(5-35 nm) silicon carbon nitride (SiCNH) dielectric as an oxidation and Cu diffusion barrier for damascene process is explored. The SiCNH cap's electrical properties, oxidation barrier performance, and the compositional depth profile analysis results showed that the scaling of the SiCNH cap is limited to 25 nm thickness. Without additional changes in current optimal SiCNH cap, 25 nm is the minimum required thickness for a reliable SiCNH cap in sub-30 nm Cu BEOL devices.