Novel Approach to High kappa (similar to 59) and Low EOT (similar to 3.8 angstrom) near the Morphotrophic Phase Boundary with AFE/FE (ZrO2/HZO) Bilayer Heterostructures and High-Pressure Annealing

Abstract

We present herewith a novel approach of equally thick AFE/FE (ZrO2/HZO) bilayer stack heterostru cture films for achieving an equivalent oxide thickness (EOT) of 4.1 angstrom with a dielectric constant (kappa) of 56 in complementary metal-oxide semiconductor (CMOS) compatible metal-ferroelectric-metal (MFM) capacitors using a high-pressure annealing (HPA) technique. The low EOT and high kappa values were achieved by careful optimization of AFE/FE film thicknesses and HPA conditions near the morphotropic phase boundary (MPB) after field cycling effects. Stable leakage current density (J < 10(-7) A/cm(2) at +/- 0.8 V) was found at 3/3 nm bilayer stack films (kappa = 56 and EOT = 4.1 angstrom) measured at room temperature. In comparison with previous work, our remarkable achievement stems from the interfacial coupling between FE and AFE films as well as a high-quality crystalline structure formed by HPA. Kinetically stabilized hafnia films result in a small grain size in bilayer films, leading to reducing the leakage current density. Further, a higher kappa value of 59 and lower EOT of 3.4 angstrom were found at 333 K. However, stable leakage current density was found at 273 K with a high kappa value of 53 and EOT of 3.85 angstrom with J < 10(-7) A/cm(2). This is the lowest recorded EOT employing hafnia and TiN electrodes that are compatible with CMOS, and it has important implications for future dynamic random access memory (DRAM) technology.