Crystalline ZrO_2-gated Ge metal-oxide-semiconductor capacitors fabricated on Si substrate with Y_2O_3 as passivation layer

摘要

By adopting an amorphous Y_2O_3 passivation layer, which provides a wide band gap and well passivates Ge surface without the presence of GeO_x, a high-permittivity (k) crystalline ZrO_2/Y_2O_3 stack was explored as the gate dielectric for Ge metal-oxide-semiconductor (MOS) devices on Si substrate. The crystalline ZrO_2 is a Ge stabilized tetragonal/cubic dielectric with the k value of 36.1 and was formed by depositing a ZrO_2/Ge/ZrO_2 laminate and a subsequent 500℃ annealing. The high-k crystalline ZrO_2/ Y_2O_3 gate stack shows promising electrical characteristics in terms of low interface trap density of 5.8 X 1011 cm"2 eV"1, negligible hysteresis, and leakage current of 5.6 X 10~(-4) A/cm~2 at gate bias of flatband voltage (V_(fb)) 1 V for equivalent oxide thickness of 1.13 nm. This gate stack not only demonstrates the eligibility for advanced Ge MOS devices but introduces a more reliable process to form a high-k crystalline gate dielectric.