Nonvolatile Field-Effect Transistors Using Ferroelectric Doped HfO2 Films

Abstract

Ferroelectrics are ideal for low power digital information storage since they can be switched purely field controlled with negligible current consumption and at the same time are nonvolatile. However, the incompatibility of classical ferroelectric materials with semiconductor technology has hindered the scaling of ferroelectric memory devices. Therefore, such devices are only used in niche applications today. In 2011, first reports indicated that hafnium oxide, which is a standard material in modern CMOS processes, can be transformed into a ferroelectric phase. Moreover, the specific properties such as much lower permittivity compared to classical perovskite based ferroelectrics and high coercive fields enable to realize scaled ferroelectric field effect transistors that show nonvolatile retention. Therefore, ferroelectric hafnium oxide can help to finally fully exploit the potential of ferroelectric memories. In this chapter, we will first show the basics of ferroelectric hafnium oxide. Then, the current understanding of the origin and technological parameters influencing the ferroelectricity in hafnium oxide are discussed. Finally, the current status and future prospects of a ferroelectric field effect transistor based memory technology are summarized.