Integrating Selective Epitaxy in Advanced Logic & Memory Devices

Abstract

In this paper, we review integration of selective epitaxy in advanced logic and memory devices. Embedded SiGe epitaxy has been adapted for logic pMOSFET fabrication from the 90 nm technology node and device performance continues to scale with higher [Ge] in the epitaxial SiGe layer. For nMOSFET performance boost, use of embedded silicon carbon (Si:C) epitaxial layer has been considered. Recent improvements in crystal quality of selective in-situ phosphorus doped Si:C epitaxy enables significant transistor drive current increase. For integration of Si:C epitaxy, effect of various thermal annealing processes on substitutional carbon incorporation and NiSi formation on Si:C epitaxy are described. Also, heavy phosphorus doping in Si and Si:C layers is discussed in terms of film resistivity and strain contribution. Selective epitaxy is being used to form elevated source/drain in DRAM memory devices where it provides immunity against short channel effects and results in improved retention time.