HfZrO2 Ferroelectric Tunneling Junction with IGZO Insertion for Unidirectional Self-rectifying Characteristics

초록

Since the discovery of ferroelectricity in hafnium oxide thin film, ferroelectric devices such as a ferroelectric field-effect transistor, ferroelectric random-access memory, and ferroelectric tunneling junction (FTJ) have attracted much interest as an emerging memory owing to high scalability and complete compatibility with complementary metal-oxide-semiconductor (CMOS) process. Among HfO2-based ferroelectric materials, hafnium-zirconium oxide (HZO) has been considered as one of the strongest candidates for the commercialization because it has stable ferroelectricity at a few nanometers thickness and low crystallization temperature for ferroelectric phase transition. FTJ is a two-terminal memory device with high density, fast switching speed, and low switching energy. FTJ cross-point arrays have been intensively researched for neuromorphic and in-memory computing applications. However, cross-point arrays have the undesirable sneaky path current which increases the power consumption and disturb the stable computing operations. To solve the sneaky path problem, indium gallium zinc oxide (IGZO) was inserted between HZO and top electrode to form a schottky contact for unidirectional rectifying characteristics. The stack of the proposed FTJ consists of bottom electrode/Al2O3/HZO/IGZO/top electrode which were all deposited only using RF sputtering. Also, all the fabrication processes were performed at the low temperature under 450 ℃, including the ferroelectricity annealing which was performed for 30 seconds under an oxygen atmosphere by rapid thermal annealing (RTA). Therefore, the proposed FTJ cross-point arrays can be applied to high-performance and low-power monolithic 3D integration for neuromorphic and in-memory computing.