Crystallization of (Hf, Zr)O2 thin films via non-heating process and their application to ferroelectric-gate thin film transistors

Abstract

HfO2-based ferroelectric materials do not necessarily require high-temperature annealing for crystallization, making them attractive for applications in transparent electronic devices on plastic or glass substrate. In this study, (Hf, Zr)O2 (HZO) films prepared via non-heating sputtering are investigated and their application to ferroelectric-gate thin-film transistors (TFTs) is demonstrated. The internal tensile stress induced by (In, Sn)O x (ITO) top-electrode deposition is found to promote the crystallization of HZO from the amorphous state to the ferroelectric phase. ITO/HZO (15–25 nm)/ITO capacitors prepared via the non-heating process exhibit ferroelectric hysteresis loops with remanent polarizations of 6–9 μC cm−2 and coercive fields of 0.6–1.1 MV cm−1. Ferroelectric-gate TFTs with a 10 nm thick ITO channel are also fabricated via the non-heating process. These TFTs show nonvolatile operation with an on/off ratio of ∼10. These findings demonstrate the potential of HZO for transparent devices on substrates with low thermal resistance prepared via the non-heating process.