The Excellent Bending Limit of a Flexible Si-Based Hf_0.5Zr_0.5O₂ Ferroelectric Capacitor with an Al Buffer Layer

Flexible Si-based Hf0.5Zr0.5O2 (HZO) ferroelectric devices exhibit numerous advantages in the internet of things (IoT) and edge computing due to their low-power operation, superior scalability, excellent CMOS compatibility, and light weight. However, limited by the brittleness of Si, defects are easily induced in ferroelectric thin films, leading to ferroelectricity degradation and a decrease in bending limit. Thus, a solution involving the addition of an ultra-thin Al buffer layer on the back of the device is proposed to enhance the bending limit and preserve ferroelectric performance. The device equipped with an Al buffer layer exhibits a 2Pr value of 29.5 mu C/cm(2) (25.1 mu C/cm(2)) at an outward (inward) bending radius of 5 mm, and it experiences a decrease to 22.1 mu C/cm(2) (16.8 mu C/cm(2)), even after 6000 bending cycles at a 12 mm outward (inward) radius. This outstanding performance can be attributed to the additional stress generated by the dense Al buffer layer, which is transmitted to the Si substrate and reduces the bending stress on the Si substrate. Notably, the diminished bending stress leads to a reduced crack growth in ferroelectric devices. This work will be beneficial for the development of flexible Si-based ferroelectric devices with high durability, fatigue resistance, and functional mobility.