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

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 (ΔI_d/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.