Elastic strain and dopant activation in ion implanted strained Si nanowires

Strained Si nanowires (NWs) are attractive for deeply-scaled complementary metal-oxide-semiconductor devices due to the combination of enhanced carrier mobility and excellent electrostatic control as was demonstrated with trigate metal-oxide-semiconductor field effect transistors. The challenge in using strained Si NWs for devices is to preserve the elastic strain during the required processing steps. In this work we investigated the influence of fundamental processing steps like patterning and dopant ion implantation on the structural and transport properties of strained Si layers and NWs on silicon-on-insulator (SOI) substrates. NWs with widths down to 35 nm, fabricated on 25 nm strained SOI and implanted to doses ranging from 5 x 10(14) to 2 x 10(15) ions/cm(2) were investigated. We show that strain conservation and a low sheet resistivity of 6.2 x 10(-4) Omega cm, close to the layer resistivity, can only be obtained if the NWs are patterned on doped layers. For NWs directly implanted to doses above 1 x 10(15) ions/cm(2), complete strain relaxation and structural disorder by solid phase recrystallization were observed. In both cases, NWs with widths smaller than 55 nm exhibit an increased specific resistivity. (C) 2010 American Institute of Physics. [doi:10.1063/1.3520665