3D Vertical Ferroelectric Capacitors with Excellent Scalability.

Three-dimensional vertically stacked memory is more cost-effective than two-dimensional stacked memory. Vertically stacked memory using ferroelectric materials has great potential not only in high-density memory but also in neuromorphic fields because it secures low voltage and fast operation speed. This paper presents the implementation of a ferroelectric capacitor comprising a vertical two-layer stacked structure composed of a titanium nitride (TiN)/aluminum-doped hafnium oxide/TiN configuration. To enhance the ferroelectric properties influenced by the active area, we propose a structure in which multiple small holes share a common pillar electrode. Comprehensive analyses using transmission electron microscopy and energy-dispersive X-ray spectroscopy were conducted to confirm the chemical composition and physical structure of the device. This newly engineered architecture demonstrated promising characteristics, including a sufficient remnant polarization, small device-to-device variations, high endurance, and excellent retention in 3D vertical structures. Moreover, this structure can be applied to one-transistor n-capacitor ferroelectric random access memory with a vertical transistor.