Two-step annealing effects on ultrathin EOT higher-k (k = 40) ALD-HfO2 gate stacks

Ultrathin HfO2 gate stacks with very high permittivity were fabricated by atomic layer deposition (ALD) and a novel two-step post-deposition annealing (PDA) technique. First, a no-cap pre-crystallization anneal degasses residual contaminations in the ALD layer, and second, a Ti-cap anneal enhances the permittivity of HfO2 by generating a cubic crystal phase. The Ti-cap layer simultaneously suppresses growth of interfacial SiO2 during annealing by absorbing residual oxygen released from HfO2. Using these techniques, the dielectric constant of the ALD-HfO2 could be enhanced to 40 for 2.4–4.0 nm HfO2 thickness.

► Dielectric constant of the ALD-HfO2 is enhanced to 40 using a two-step PDA. technique. ► ALD-related contaminants in HfO2 layer suppress generation of high permittivity cubic phase. ► Reduction of the contaminants by first PDA enhances cubic phase generation by second PDA.