Electrical properties of highly reliable plug buffer layer for high-density ferroelectric memory

Abstract

A CoSi2 buffer layer was prepared in polycrystalline silicon (polysilicon) plug for preventing an undesired microvoid between the polysilicon plug and Ir/Ti diffusion barrier. Since the microvoid generates random function fail, resulting in low wafer yield of a 4 Mb ferroelectric random access memory device, we developed the thermally stable CoSi2 buffer layer for eliminating the random single bit fails. The ferroelectric capacitors using the CoSi2 buffer layer showed a low contact resistance of 96 Ω per contact in 1k serial contact array with contact size of 0.6 μm, and also exhibited great ferroelectric properties such as remnant polarization and coercive voltage of 20 μC/cm2 and 1.2 V, respectively. Scanning electron microscopy analyses confirmed that no microvoid was formed between the interface between the Ir/Ti barrier layer and the CoSi2 buffer layer.