Fabrication and characterization of a trilayer germanium nanocrystal memory device with hafnium dioxide as the tunnel dielectric

Abstract

We have fabricated trilayer insulator metal-insulator-semiconductor (MIS) structures consisting of hafnium dioxide (HfO2) as the high-κ tunnel dielectric, a germanium (Ge) nanocrystal middle layer formed by sputtering and subsequent rapid thermal annealing, and a silicon dioxide cap layer. Capacitance-voltage (C-V) measurements of such structures show a clockwise hysteresis on n-type silicon substrates, demonstrating the charge storage capability of the device. Transmission electron microscopy (TEM) analysis shows no significant penetration of Ge into the silicon substrate. The data retention capability of the MIS structures was characterized using capacitance-time (C-t) measurements. The charge retention capability of the device with HfO2 as the tunnel dielectric was found to be two times better than that of a similar structure control device with silicon dioxide as the tunnel dielectric. © 2004 Elsevier B.V. All rights reserved.