Effect of annealing temperature on electrical and reliability characteristics of HfO₂/porous low-k dielectric stacks

Atomic layer deposited thin HfO₂ film has been demonstrated to act as a pore-sealing layer and a Cu diffusion barrier layer used in porous low-k dielectrics. This study investigates the effect of annealing temperature on the electrical characteristics and reliability of the dielectric stacks with HfO₂ and porous low-k films. The experimental results reveal that annealing improved electrical performance and reliability, but increased the dielectric constant. However, the resulting dielectric constant of the annealed HfO₂/porous low-k dielectric stacks following oxygen plasma treatment was still lower than that of the dielectric stacks without annealing, indicating that annealing improved the properties of HfO₂/porous low-k dielectric stacks. Annealing at 400 °C improved electrical characteristics, reliability, and Cu barrier performance more than did annealing at 600 °C because at 600 °C annealing, the grain boundaries of the crystallized HfO₂ film provide a conduction path and cause the breakage of the porous low-k film. However, the HfO₂/porous low-k dielectric stacks that were annealed at 600 °C exhibited greater resistance against damage by oxygen plasma.