Stabilization of Morphotropic Phase Boundary in Hafnia via Microwave Low-Temperature Crystallization Process for Next-Generation Dynamic Random Access Memory Technology

Abstract

The morphotropic phase boundary (MPB), which arises from the combination of antiferroelectric and ferroelectric phases, demonstrates the highest dielectric constant (κ) compared to other phases. This emphasizes its potential as a leading contender for dielectric films in future dynamic random access memory (DRAM) capacitors. MPB-based high-κ materials using hafnia have shown a trade-off between equivalent oxide thickness (EOT) and leakage current density (Jleak) when the crystallization temperature increases with scaling the thickness. Herein, a microwave annealing (MWA) method that can achieve low-temperature crystallization below 350 °C is employed. The purpose of this method is to mitigate the trade-off relationships and achieve the strict criteria of current DRAM capacitors. These criteria include low EOT (less than 4 Å) and Jleak (less than 10−7 A cm−2 at 0.8 V) characteristics. The MWA is capable of relatively low-temperature annealing by supplying energy to the films through both thermal energy and dipole vibration energy. As a result, a record-low EOT of 3.76 Å and a low leakage current characteristic of 4.2 × 10−8 A cm−2 at 0.8 V are achieved concurrently. It is confident that the research can be important in addressing the challenges associated with reducing the size of next-generation DRAM capacitors.