The effects of process temperature on the work function modulation of ALD HfO₂ MOS device with plasma enhanced ALD TiN metal gate using TDMAT precursor

Abstract

We have investigated the effects of metal gate process temperature on the effective work function (W-eff) of MOS devices with all ALD HfO₂/TiN gate stack and its correlation with grain size of PEALD TiN metal gate is presented with other electrical characteristics. Ti precursor and reactant were used with tetrakis-dimethyl-amino titanium (TDMAT) and H₂/N₂ mixture for TiN while tetralds-ethylmethyl-amino hafnium (TEMA-Hf) and H₂O were used for HfO₂. With increasing TiN deposition temperature, the W-eff of TiN electrode is positively shifted up to similar to 200 meV while EOT is kept as 1.2 nm. These findings could be attributed to the combining effects from crystal structure charige (i.e., increased grain size) and different chemical composition. Unlike PVD TiN system, in ALD TiN system, higher V-FB is observed with increasing Ti ratio in the film, ascribed to the small amount of carbon residue (6-9 at%) within the TDMAT precursor.