Ge-stabilized tetragonal ZrO2 as gate dielectric for Ge metal-oxide-semiconductor capacitors fabricated on Si substrate

A Ge-stabilized tetragonal ZrO2 (t-ZrO2) film formed by incorporating Ge atoms thermally driven from an underlying Ge layer into a ZrO2 film was investigated as the gate dielectric for Ge metal-oxide-semiconductor (MOS) capacitors fabricated on a Si substrate. A sole t-ZrO2 film on Ge is not eligible for the gate dielectric because of the poor interface quality. By using a thermally-grown ultrathin GeO2 film as an interfacial layer, the t-ZrO2/GeO2/Ge stack shows improved interface characteristics and a permittivity (kappa) value of 36.6 for the t-ZrO2. In addition, the stack also demonstrates good leakage current since the amorphous GeO2 layer terminates grain boundary channels in the crystalline ZrO2. Further leakage current suppression can be achieved by a H-2 annealing of the t-ZrO2/GeO2/Ge stack since the defects at grain boundaries can be effectively passivated, which makes a leakage current of 1.08x10(-6) A/cm(2) at V-FB-1 V for effective oxide thickness of 1.66 nm and paves an alternative avenue to develop a high-performance crystalline gate dielectric for Ge MOS devices. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3455904]