5.1 Å EOT and low leakage TiN/Al2O3/Hf0.5Zr0.5O2/Al2O3/TiN heterostructure for DRAM capacitor

Abstract

Further scaling of dynamic random-access memory (DRAM) faces critical challenges because of the lack of materials with both high dielectric constant and low leakage. In this work, engineering Hf1−xZrxO2 (HZO) films to the morphotropic phase boundary (MPB) and inserting Al2O3 interface layers with a wide bandgap are utilized to overcome this bottleneck. By tuning Zr composition and the woken-up process, the ratio of tetragonal and orthorhombic phases is manipulated to achieve the desired high dielectric constant MPB state. On this basis, Al2O3 ultrathin layers are inserted to further enhance the dielectric constant as well as reduce the leakage current. As a result, a high dielectric constant of ∼ 46.7 (equivalent oxide thickness ∼ 5.1 Å) and low leakage current density (<10−7 A/cm2 at ±0.5 V) are achieved in TiN/Al2O3 (0.2 nm)/Hf0.5Zr0.5O2 (5.6 nm)/Al2O3 (0.3 nm)/TiN capacitors. Furthermore, long dielectric breakdown time of the heterostructure confirms its application potential. These results are useful for developing next generation DRAM capacitor devices.