Optimization of HfSiON using a design of experiment (DOE) approach on 0.45 V Vt Ni-FUSI CMOS transistors

We report for the first time that the optimization of a HfSiON process on Ni-FUSI devices is best tackled using a design of experiments (DOE [Myers RH, Montgomery. Response surface methodology. New York, DC: Wiley; 1995]) approach. We show that a DOE allows for directly linking process parameters to relevant short channel performance metrics. By tuning the SiO2 thickness, HfSiO thickness, Hf concentration, nitridation parameters and by using response surface modeling (RSM), we report an improvement of 12%/17% in nMOS/pMOS drive current (Idsat 600/255 uA/μm at Ioff = 20 pA/μm and Vdd = 1.1 V) over our reference process. In parallel, we demonstrate that by selecting the right parameters, plasma nitridation can outperform thermal nitridation with NH3. We believe that this new approach will be useful for device engineers and can be easily applied.