Pushing Sputtered HfO2-Based Ferroelectrics toward BEOL Compatibility

Abstract

In this work, we investigate the back-end-of-line (BEOL) compatibility of the TiN/Hf1-xZrxO2 (HZO)/TiN thin-film capacitors by exploiting the effect of sputtering power, ZrO2 content and process pressure. The variation of double remanent polarization (2Pr) suggests a crystal phase transformation in the HZO film when the sputtering power is altered. A change in the dielectric constant also supports this behavior. After tuning the process pressure, we could lower the required thermal budget for crystallization to 400°C, which is thermally compatible with BEOL processes. Moreover, the optimal sputtering parameters could reach 2Pr of 36 μC/cm² with an endurance of up to 10⁷ cycles. High 2Pr and good endurance achieved with low-temperature annealing is a breakthrough for sputtered HfO2-based thin films and shows a promising future for integrating sputtered HZO into BEOL processes.