A comparative study of gate first and last Si MOSFETs fabrication processes using ALD beryllium oxide as an interface passivation layer

Extending our previous study demonstrating that ALD-BeO hi-k on Si and III-V exhibits excellent electrical characteristics, we discuss the advantages of using BeO as the interface passivation layer (IPL) in silicon metal-oxide-semiconductor field effect transistors (Si-MOSFETs) from the perspective of the gate-first and the gate-last process. By comparing three hi-k stacks, BeO/HfO₂, Al₂O₃/HfO₂, and SiO₂/HfO₂, fabricated using the gate first and gate last processes, we demonstrate that for both processes, BeO/HfO₂ significantly outperforms the other stacks in terms of drive current, transconductance (G_m), subthreshold swing (SS), inversion capacitance, and mobility.