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

We have investigated the effects of metal gate process temperature on the effective work function (Weff) 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 tetrakis-ethylmethyl-amino hafnium (TEMA-Hf) and H2O were used for HfO2. With increasing TiN deposition temperature, the Weff of TiN electrode is positively shifted up to ~200meV while EOT is kept as 1.2nm. These findings could be attributed to the combining effects from crystal structure change (i.e., increased grain size) and different chemical composition. Unlike PVD TiN system, in ALD TiN system, higher VFB is observed with increasing Ti ratio in the film, ascribed to the small amount of carbon residue (69at%) within the TDMAT precursor. Display Omitted HfO2-MOS device with ALD TiN using TDMAT precursor and H2/N2 mixture shows higher VFB by 200mV with 1.2nm EOT.TDMAT ALD TiN shows higher VFB with increasing [Ti]/[Ti+N2] ratio due to the combining effects of carbon residue from the precursor and increased grain size.