Attomolar streptavidin and pH, low power sensor based on 3D vertically stacked SiNW FETs

Abstract

3D vertically stacked silicon nanowire (SiNW) field effect transistors (FET) with high density arrays (up to 7×20) of fully depleted and ultra-thin (15-30 nm) suspended channels were fabricated by a top-down CMOS compatible process on silicon on insulator (SOI). The channels can be wrapped by conformal high-κ gate dielectrics (HfO2) and their conductivity can be excellently controlled either by a reference electrode or by three local gates; a backgate (BG) and two symmetrical Pt side-gates (SG) offering unique sensitivity tuning. Such 3D structure has been (3-Aminopropyl)-triethoxysilane (APTES) functionalized and biotynilated for pH and streptavidin (protein) sensing, respectively. An ultra-low concentration of 17 aM of streptavidin was measured, the lowest ever reported in literature. Extremely high quasi-exponential drain current responses (ΔId/pH) of ~0.70 dec/pH were measured for structures with APTES functionalized SiO2 gate dielectrics when operated in the subthreshold regime. Also, high drain current responses > 20 μA/pH and high sensitivities (S ~ 95%) were measured for structures with a native oxide gate dielectrics when operated in the strong-inversion regime.