Pulsed laser-ablation deposition of thin films of molybdenum silicide and its properties as a conducting barrier for ferroelectric random-access memory technology

Abstract

We report on the feasibility of using molybdenum silicide as a conducting barrier for integration of ferroelectric lead zirconate titanate capacitors on Si. Thin films of MoSi2 were deposited by pulsed laser-ablation deposition (PLD). The silicide films showed a structural transition from amorphous to orthorhombic to tetragonal phase as the temperature of deposition was changed from room temperature to 900 °C. The four-probe resistivity and surface roughness of the films decreased with an increase in the deposition temperature and crystallinity of the phase. Ferroelectric (La, Sr)CoO3/Pb(Nb, Zr, Ti)O3/(La, Sr)CoO3 capacitors were grown on Si/poly Si/MoSi2, and Si/poly Si/MoSi2/Pt structures. Transmission electron microscopy (TEM) studies of the MoSi2/LSCO and MoSi2/Pt/LSCO heterostructures indicated the formation of a thin layer of SiO2. In the case of Pt/MoSi2, Pt reacts with the silicide and forms PtSi, consuming the entire platinum layer and, thus, makes it unsuitable as a composite barrier. Electrical testing of the LSCO/PNZT/LSCO capacitors through capacitive coupling showed desirable ferroelectric properties on these substrates.