Arsenic-doped epitaxial source/drain regions for nmos

Abstract

Techniques are disclosed for providing an integrated circuit structure having NMOS transistors including an arsenic-doped interface layer between epitaxially grown source/drain regions and a channel region. The arsenic-doped interface layer may include, for example, arsenic-doped silicon (Si:As) having arsenic concentrations in a range of about 1E20 atoms per cmto about 5E21 atoms per cm. The interface layer may have a relatively uniform thickness in a range of about 0.5 nm to full fill where the entire source/drain region is composed of the Si:As. In cases where the arsenic-doped interface layer only partially fills the source/drain regions, another n-type doped semiconductor material can fill remainder (e.g., phosphorus-doped III-V compound or silicon). The use of a layer having a high arsenic concentration can provide improved NMOS performance in the form of abrupt junctions in the source/drain regions and highly conductive source/drain regions with negligible diffusion of arsenic into the channel region.