On La-doped HZO as a high-<i>k</i> dielectric for DRAM: Low EOT and approaches for its improvement

Abstract

Despite the great potential of the hafnium zirconium oxide (HZO)-based ferroelectrics for the emerging non-volatile ferroelectric memories, it provides also a material solution to the existing technological challenge arising for DRAM memory. In this work, we explore the possibility of using the La-doping of HZO to ensure low leakages along with high dielectric permittivity k and low equivalent oxide thickness (EOT) and the technological and operational approaches, including rapid thermal annealing and electric-field cycling, for their further improvement. We show that fully ALD grown TiN/La-HZO/TiN devices formed in the temperature budget not exceeding backend-of-line-compatible 400 °C easily provide the EOT value of 0.86 nm at the La-HZO thickness of 10 nm. The optimal cycling and annealing conditions (3–4 V@550 °C) provide the EOT as low as 0.46 nm. Considering also the rather low leakage currents, significantly less than 10−7 A/cm2, and moderate energy loss, this result makes the La-HZO films promising for the future DRAM technology.