Elastic strain and dopant activation in ion implanted strained Si nanowires

Abstract

Strained Si nanowires ͑NWs͒ are attractive for deeply-scaled complementary metal-oxidesemiconductor 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 ͑SOI͒ substrates. NWs with widths down to 35 nm, fabricated on 25 nm strained SOI and implanted to doses ranging from 5 ϫ 10 14 to 2 ϫ 10 15 ions/ cm 2 were investigated. We show that strain conservation and a low sheet resistivity of 6.2ϫ 10 −4 ⍀ 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 ϫ 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.

Top-down fabricated silicon nanowires under tensile elastic strain up to 4.5%

“…1a is the length L etched underneath the buried oxide, beyond the outer frame of the structure. The released bridges relax in the transverse directions 16 while transferring longitudinally strain from the two pads to the NW located at the bridge centre. Assuming a constant silicon layer thickness, the cross-sectional dependency of the stress distribution used to determine the strain enhancement in the NWs can be reduced to a dependency on the length ratio, (B − A)/A, and the width ratio, b/a.…”

p-Type Ion Implantation in Tensile Si/Compressive Si0.5Ge0.5/Tensile Strained Si Heterostructures

“…Although strained SOI layers were proved to be stable up to 1000 • C, 23 the SiGe layers relax through the formation and movement of dislocations. Therefore, before analysing the properties of implanted SiGe layers, we have first investigated the thermal stability of un-implanted layers.…”

(Invited) Si Nanowire Tunnel FETs for Energy Efficient Nanoelectronics

“…In doing so the strain across the patterned wires relaxes, while the strain along the wires maintains. Therefore, the nanowires are uniaxially strained along the wire direction, which was demonstrated theoretically by 2D finite element simulations (13) and experimentally by Raman measurements (14). Figure 1 illustrates the TFET fabrication process.…”