Aya Seike

Strain-induced transconductance enhancement by pattern dependent oxidation in silicon nanowire field-effect transistors

Transconductance (gm) enhancement in n-type and p-type nanowire field-effect-transistors (nwFETs) is demonstrated by introducing controlled tensile strain into channel regions by pattern dependent oxidation (PADOX). Values of gm are enhanced relative to control devices by a factor of 1.5 in p-nwFETs and 3.0 in n-nwFETs. Strain distributions calculated by a three-dimensional molecular dynamics simulation reveal predominantly horizontal tensile stress in the nwFET channels. The Raman lines in the strain controlled devices display an increase in the full width at half maximum and a shift to lower wavenumber, confirming that gm enhancement is due to tensile stress introduced by the PADOX approach.

Transconductance enhancement of nanowire field-effect transistors by built-up stress induced during thermal oxidation

The authors report the enhancement of transconductance in nanowire field effect transistors due to build-up tensile stress during thermal oxidation. To evaluate the effect of stress, nanowires were thermally oxidized at (A) 900°C∕15min, (B) 850°C∕1h, and (C) 850°C∕1h with a subsequent 1000°C annealing. The transconductance of sample B is enhanced 2.6 times compared to sample A. No enhancement of transconductance is observed in sample C. The Raman spectra indicate tensile stress in sample B and compressive stress in sample C. This establishes that gm enhancement is due to the build-up tensile stress in nanowires, but is diminished by viscoelastic relaxation.

Transconductance enhancement of Si nanowire transistors by oxide-induced strain

Transconductance (gm) enhancement in n-type and p-type nanowire field-effect-transistors (nwFETs) is demonstrated by introducing controlled tensile strain into channel regions by pattern dependant oxidation (PADOX). Values of gm are enhanced relative to control devices by a factor of 1.5 in p-nwFETs and 3.0 in n-nwFETs. Strain distributions calculated by a three-dimensional molecular dynamics simulation reveal predominantly horizontal tensile stress in the nwFET channels. The Raman spectra features in the strain controlled devices display an increase in the full width half maximum, and a shift to lower wavenumber confirming that gm enhancement is due to tensile stress introduced by the PADOX approach.

Evaluation of phosphorus diffusion in the confined nano-wire under the influence of Si/SiO 2 interface

Diffusion of phosphorus is studied by means of electrical measurement of the Si-wire devices and SIMS profiles of bulk SOI. The conductivity of Si-wire decreases as the thermal budget increases. The sample of 80 nm in the designed width (Wmask), of which the actual width after the oxidation is 57.4 nm, has higher conductivity, which is the factor of 3 to 4.5, with respect to the theoretical value of bulk Si. We assume that the stress applied from the peripheral SiO2 influence on the phosphorus diffusion in Si. Segregation of phosphorus ions at both cap-SiO2/Si(SOI) and Si(SOI)/SiO2(BOX) is recognized, however, no dependency of SIMS profiles on the thermal budget is confirmed. Dose loss of phosphorus due to the diffusion into the cap-SiO2 is about 1*1019 cm-3. The result of dependency of conductivity on the thermal budged doesnpsilat coincide with the data of SIMS profiles. This is because the SIMS profile of bulk sample doesnpsilat provide the lateral information nor reflect the effect of stress from the peripheral SiO2 film. Further investigation will be needed to reveal the relation between the size effect on the conductivity and the stress from the peripheral SiO2.