Effective formation of interface controlled Y2O3 thin film on Si(100) in a metal-(ferroelectric)-insulator-semiconductor structure

Abstract

Yttrium was deposited on the chemical oxide of Si and annealed under vacuum to control the interface for the formation Of Y2O3 as an insulating barrier to construct a metal-ferroelectric-insulator-semiconductor structure. Two different pre-annealing temperatures of 600 and 700 degrees C were chosen to investigate the effect of the interface state formed after the pre-annealing step on the successive formation of Y2O3 insulator and Nd2Ti2O7 (NTC) ferroelectric layer through annealing under an oxygen atmosphere at 800 degrees C. Pre-anneal treatments of Y-metal/chemical-SiO2/Si at 600 and 700 degrees C induced a formation of Y2O3 and Y-silicate, respectively. The difference in the pre-anneal temperature induced almost no change in the electrical properties of the Y2O3/interface/Si system, but degraded properties were observed in the NTO/Y2O3/interface/Si system pre-annealed at 600 degrees C when compared with the sample pre-annealed at 700 degrees C. C-V characteristics of the NTO/Y2O3/Si structured system showed a clockwise direction of hysteresis, and this gap could be used as a memory window for a ferroelectric-gate. A smaller hysteric gap and electrical breakdown values were observed in the NTO/Y2O3/Si system pre-annealed at 600 degrees C, and this was due to an unintentional distribution of the applied field from the presence of an interfacial layer containing Y-silicate and SiO2 phases. (C) 2008 Elsevier B.V. All rights reserved.