Trade-off between interfacial charge and negative capacitance effects in the Hf-Zr-Al-O/Hf0.5Zr0.5O2 bilayer system

Abstract

Recently, negative capacitance (NC) effect in the dielectric/ferroelectric (DE/FE) bilayer system has received significant attention due to its potential in achieving sub- 60 mV/decade subthreshold swing in FETs as well as extremely large capacitance density in dynamic random-access memory (DRAM). However, such reports, to date, are primarily based on conventional perovskite FE materials which are not compatible with the present CMOS technology. Herein, we study the interfacial charge density (σi)and negative capacitance (NC) effect in CMOS compatible Hf-Zr-Al-O (DE) /Hf0.5Zr0.5O2 (FE) bilayer system. The DE layer of various thicknesses (5–20 Å) was deposited on the top of FE layer (100 Å) and the DE layer thickness was found to play a crucial role in determiningσi. The NC effect in the aforesaid DE/FE system was suppressed due to the contribution of σi. The σiat the interface of the DE layer and FE layer was found to be in the range of −0.57 Cm−2 to −0.18 Cm−2 for the DE thickness range of 5–20 Å.