(The) thermal stability of hafnia-based ferroelectric devices for transistor with excellent high temperature characteristics

Abstract

Recently, the demand for data storage devices such as the solid-state drives and data centers are rapidly increasing due to the development in the IoT, the AI, and the big data. Various attempts are being made to develop next-generation semiconductor devices to keep pace with such an increase in demand, and ferroelectric transistors have device characteristics such as non-volatility and low operation voltage. Studies on the three-dimensional ferroelectric NAND flash using the ferroelectric and ferroelectric transistors in cell stacks or arrays have been reported. However, 3D NAND flash requires a post-annealing process (>650° C) after ion implantation to form a polycrystalline silicon channel and an oxide layer, and ferroelectric may suffer property degradation due to additional thermal budget. In addition, electrical analysis and tools that can analyze the thermal stability of ferroelectrics subjected to the post-annealing have not been clearly presented. Therefore, research and development for the thermally robust ferroelectric are needed. In this study, we report a study on a thermally stable ferroelectric thin film using Zr and Al dopants, and 1nm-thick aluminum oxide and aluminum nitride layers in hafnia ferroelectrics. Through physical and electrical analysis, it was demonstrated through physical and electrical analysis that the degradation of hafnia ferroelectrics such as the leakage current and the phase transitions to the non-ferroelectric phase can suppress the degradation of ferroelectrics by controlling the doping concentration. Furthermore, the effect of the insertion layer (AlO, AlN) was observed and the ferroelectric degradation characteristics were evaluated. Through this, it was verified that the dopants and the insertion layers could suppress the ferroelectric deterioration caused by the post-annealing.