Stabilizing Antiferroelectric‐Like Aluminum‐Doped Hafnium Oxide for Energy Storage Capacitors

Herein, a systematic study of aluminum-doped hafnium oxide to utilize its antiferroelectric-like (AFE) properties for energy storage applications is done. The doping concentration of aluminum is optimized to obtain the AFE-like phase. In addition, the impact of the postmetallization annealing temperature on the energy storage properties of the materials is studied. Metal-insulator-metal capacitors are fabricated by varying the doping concentration of the Al in HfO2 from 1.9 to 6.2 at% with a constant thickness of 10 nm by atomic layer deposition. The devices are rapid thermal annealed by varying the annealing temperature from 650 to 800 °C for 20 s. Polarization measurements indicate a clear phase transformation from ferroelectric (FE) to AFE to paraelectric phase with the increase of doping concentration in the polarization measurements. The planar antiferroelectric devices have an energy storage density of 30 J cm-3 with 76% efficiency after 105 cycles. The storage density can be further increased by a factor of 16.5 using area-enhanced substrates to 500 J cm- 3 at 73% efficiency. The endurance characteristics are studied for both planar and 3D capacitors which are found to be stable up to 108 cycles.