Junction for Deep Sub-100 NM Mos: How Far Will Ion Implantation Take Us?

We analyze the requirements that the International Technology Roadmap for Semiconductors (ITRS) implicitly imposes on the two-dimensional source/drain (SD) dopant profile and translate the results into implant parameters (energy, dose, peak concentration). We do this by determining the voltage drop that the SD current develops across the three main (exclusive of the channel) resistive components in the current path: the spreading resistance int he extension region; the metal-semiconductor contact; and the resistance in the link-up region where the SD-region meets the channel. The largest resistance occurs in the link-up region, followed by the resistance of the contact; the extension contribution is the smallest. The extension resistance requirement can be satisfied by ion-implantation for all generations of the ITRS. The link-up region requires very abrupt lateral profiles, not demonstrated so far by ion-implantation. It is found that such resistance cannot be reduced without impacting the intrinsic device behavior. The contact eventually necessitates dopant concentrations in excess of solid solubility and for NMOS in excess of the fundamental limit of dopant activation.