Atomic layer deposited TiN capping layer for sub-10 nm ferroelectric Hf0.5Zr0.5O2 with large remnant polarization and low thermal budget

Ferroelectric Hf0.5Zr0.5O2 (HZO) thin films has attracted a large amount of interests in academia and industry. The scaling of the HZO thickness down to the sub-10 nm region with a low thermal budget is essential in practical applications. However, pronounced ferroelectricity in sub-10 nm HZO thin films prepared at a low process temperature is rarely reported. In this paper, significant ferroelectricity is reported in 6 nm HZO thin films by the TiN capping electrode prepared by atomic layer deposition (ALD). Capping the ALD TiN layer leads to the crystallization of an as-deposited amorphous HZO thin film to the ferroelectric orthorhombic phase. The post-annealing treatment at a low temperature of 400 °C contributes to a record remnant polarization (2Pr) of ∼ 51.2 μC/cm2 in sub-10 nm HZO. The mechanisms of the TiN capping effect are investigated based on the TiN capping layers prepared by ALD and sputtering. The distinct ferroelectric properties can be attributed to the formation of a large in-plane tensile stress and the TiOxNy mixed phase by the ALD TiN capping layer. The realization of the low thermal budget and high 2Pr in sub-10 nm HZO thin films by the ALD TiN capping layer is highly promising for next-generation ferroelectric applications.