Ultrathin Ferroelectricity and Its Application in Advanced Logic and Memory Devices

Abstract

Compared to archetypical perovskites, HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based ferroelectric materials are process-compatible with advanced CMOS transistors. As a result, they promise to bring ferroelectric technologies into widespread applications. At the same time, ferroelectricity in these materials is also different. In conventional perovskites, the polarization becomes weaker as the thickness is decreased due to `size effects'. Balking this conventional trend, our recent work has shown that ferroelectricity in HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> in fact enhances as the thickness goes down. The ferroelectricity can be demonstrated even in a 1 nm film, which is just two-unit cells! Ferroelectric tunnel junction results with 1 nm ferroelectric. In addition, Negative Capacitance transistors have been demonstrated with just 18A thick ferroelectric material - the same thickness of high-dielectric used in today's advanced transistors. These results demonstrate that, unlike conventional ferroelectrics, thickness scaling is not a bottleneck for HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> based ferroelectrics, paving the way for their integration in the most advanced logic and memory devices.