Characterization of silicon–carbon alloy materials for future strained Si metal oxide semiconductor field effect transistors

Abstract

N type metal oxide semiconductor field effect transistors (NMOSFETs) using strained silicon–carbon alloy (Si1−xCx) surface channels are reported in this work. Tensile-strained Si1−xCx layers with substitutional carbon content up to ~1% were epitaxially grown on (100) Si substrates by ultra-high vacuum chemical vapor deposition, using silane and methylsilane as the silicon and carbon sources, respectively. NMOSFETs were fabricated using standard MOS processing with reduced thermal treatment in order to minimize the possibility of strain relaxation. A reciprocal space mapping method was used to analyze strain distribution in the silicon–carbon alloy thin films on Si substrates. The election inversion layer mobilities of the Si1−xCx and Si control devices at room temperature are comparable. This is in contrast to the electron mobility enhancement observed in NMOSFETs fabricated using tensile-strained Si grown on relaxed Si1−xGex layers. At low temperatures, the electron inversion layer mobility of Si1−xCx devices is lower than that of the Si controls, and appears to be affected by Coulomb as well as possibly by random alloy scattering.