In situ UHVEM irradiation study of intrinsic point defect behavior in Si nanowire structures

Abstract

Si nanowire‐based Tunnel‐Field Effect Transistor (TFET) characteristics are intensively studied as function of nanowire diameter and doping. A significant reduction of B diffusion with decreasing nanowire diameter is e.g. observed and attributed to reduced transient enhanced diffusion close to the nanowire surface caused by the recombination and out‐diffusion of excess self‐interstitials. In an Ultra High Voltage Electron Microscope (UHVEM), the formation of self‐interstitial clusters can be studied in situ while varying e‐beam flux, irradiation temperature, impurity concentration and capping layers surrounding the nanowires.Results are presented on {113}‐defect formation in Si nanowires with diameters between 40 and 500 nm. The Si nanowires are embedded in SiO2 and are etched into an epitaxial Si stack on a heavily As doped Si substrate. The top layer of the epitaxial stack is in situ B doped or B implanted. In situ UHVEM studies are performed on focused ion beam prepared cross‐section samples, irradiating with different fluxes of 2 MeV electrons between room temperature and 375 °C. A strong dependence of {113}‐defect formation on nanowire radius and doping is observed. The observations are compared with simulations based on quasi‐chemical reaction rate theory. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Impact of dopants and silicon structure dimensions on {113}‐defect formation during 2 MeV electron irradiation in an UHVEM

“…Irradiations are performed on FIB prepared cross-section samples between room temperature and 375 • C, using a 2 MeV electron beam. Some first results on the same structures were published elsewhere [16,17].…”

“…3. More experimental results on the nanowires of the present study can be found in references [16] and [17].…”

“…While the 50 nm sample is interstitial-rich for different strengths of a vacancy sink ( √ k XV C X ), the 200 nm sample is always vacancy-rich explaining why no {113}-defects are formed in thicker p + samples. Other simulations based on equations (3), (10) and (11) can be found elsewhere [13,16,17].…”

“…Equations (3), (10) and (11) allow to simulate the effect of k XI C X and k XV C X for different irradiation temperatures and sample thicknesses [13,16,17].…”

In situUHVEM study of {113}-defect formation in Si nanowires

“…A first set of about 150 nm thick cross-section specimens for in situ irradiation was prepared by focused ion beam (FIB) both in the [110] and [100] orientations taking care that most of the nanowires were embedded into the sample thickness. Results on these samples have been published elsewhere [18][19][20].…”