Annealing Study of ALD Deposited Ferroelectric Aluminum-doped Hafnium Oxide

With the acquisition of a Savannah ALD tool at RIT, it is now possible to deposit ferroelectric Al-doped HfO2 (Al:HfO2) in the SMFL. Recipes for Al:HfO2 have been developed using tetrakis(dimethylamido)hafnium(IV) (TDMAHf) as a Hafnium precursor, and trimethyl aluminum (TMA) as an Aluminum precursor. Various percentages of Al in the Al:HfO2, controlled by the number of TMA cycles during the ALD deposition, were deposited in order to observe the effect of Al concentration on ferroelectricity. To determine the dependence of ferroelectricity on annealing conditions, samples underwent rapid thermal annealing steps at varying temperatures and times. The dependence of a top TiN electrode being present during then annealing step on ferroelectricity was also observed, as both Post-Metallization Anneal (PMA) and a Post-Deposition Anneal (PDA) process steps were performed for both Al concentration and annealing conditions. It was found that ferroelectricity was only observed in PDA devices, as it is likely that the top TiN layer was absorbing enough heat to prevent the domain sizes from growing in the Al:HfO2 layer in the PMA devices. It was also observed that a longer annealing time yields higher remnant polarization values at similar coercive voltage values, which is likely due to larger domain sizes resulting from the longer anneal