Effects of an interfacial dead layer on the ferroelectric HfZrOx films for low thermal budget

It is important to obtain ferroelectric HfZrOx (HZO) films at low crystallization temperatures to ensure compatibility with low-temperature processes. This study investigates the origin of degradation in ferroelectric properties of ferroelectric films at low crystallization temperatures, by modifying the bottom electrodes and HZO thicknesses. The TiN/HZO/TiN and W/HZO/W stacks exhibit no or very weak ferroelectric properties at all HZO thicknesses evaluated at a crystallization temperature of 300 °C. However, W/HZO/Pt exhibits ferroelectric properties for most of the range of HZO thicknesses evaluated, and exhibits a sufficient switchable polarization (2Pr) value of 39.83 μC/cm² at a HZO thickness of 12 nm. It is expected that this may be attributed to an interfacial dead layer that suppresses the formation of the ferroelectric phase. The formation of interfacial dead layer is indirectly confirmed using the pulse-switching technique. As a result, the HZO film with the Pt electrode exhibits a large interfacial capacitance compared with that of TiN and W electrodes, implying that the formation of the interfacial dead layer is minimized. These results indicate that a low thermal budget for ferroelectric HZO devices can be achieved by selecting an appropriate fabrication process that minimizes the formation of an interfacial layer.