Electrical characteristics of floating-gate memory devices with titanium nanoparticles embedded in gate oxides.

The electrical characteristics of titanium (Ti) nanoparticle-embedded metal-oxide-semiconductor (MOS) capacitors and metal-oxide-semiconductor field effect transistors (MOSFETs) with blocking Al2O3 layers are studied in this work. Ti nanoparticles were synthesized by a thermal deposition of Ti and by a subsequent thermal annealing procedure. The capacitance versus voltage (C-V) curves obtained for a representative MOS capacitor embedded with Ti nanoparticles exhibit large flat-band voltage shifts, demonstrating the presence of charge storages in the Ti nanoparticles. The counterclockwise hysteresis and flat-band voltage shift observed from the C-V curves imply that electrons are stored in a floating gate layer consisting of the Ti nanoparticles present between the tunneling oxide and control oxide layers in the MOS capacitor and that these stored electrons originate from the p-type Si substrate in inversion condition. Moreover, the source/drain current versus gate voltage curves for the Ti nanoparticle-embedded MOSFETs and the threshold voltage shift characteristics of program/erase time, endurance and retention are analyzed in this paper.