Ferroelectricity in hafnium oxide: CMOS compatible ferroelectric field effect transistors

Abstract

We report the discovery of ferroelectricity in crystalline hafnium silicon oxide. If HfO2 based thin films, at a composition where the tetragonal phase is not yet stable, are crystallized in presence of a cap, the formation of an orthorhombic phase is observed. o-HfO2 shows a piezoelectric response, while a polarization measurements exhibit a remanent polarization above 10 µC/cm2 at a coercive field of 1 MV/cm, confirming this phase to be ferroelectric. Transistors fabricated with this material exhibit a permanent and switchable shift of the threshold voltage, allowing the realization of CMOS-compatible ferroelectric field effect transistors (FeFET) with sub 10 nm gate insulators for the first time

Modeling and simulation of low power ferroelectric non-volatile memory tunnel field effect transistors using silicon-doped hafnium oxide as gate dielectric

“…The silicon-doped HfO 2 is utilized as ferroelectric layer due to its unique property of exhibiting the ferroelectricity even in a 5 nm thick, thin film [14,15]. For the model verification, we have used 10 nm of Si:HfO 2 with 9 lC=cm 2 remanent polarization and 1.1 mV/cm coercive field [6]. We will discuss how the relatively high coercive field and remanent polarization guarantee a large memory window (and retention time) in the Ferroelectric Memory TFET.…”

“…The properties of two wellknown perovskite ferroelectrics, Lead Zirconate Titanate (PZT) and Strontium Barium Titanate (SBT), is compared with Si:HfO 2 in Table 1. The recently discovered ferroelectric thin film, Si:HfO 2 [28,6], has a relatively high coercive field that ensures a large memory window [29][30][31][32][33][34][35][36][37][38][39].…”

“…However, it should be noted that a thin layer of HfSiO forms at the interface during the deposition and annealing of the Si:HfO 2 which is called the dead layer. The dead layer performs no ferroelectricity, and it behaves like a buffer layer causing reduced memory window [6,28]. As the dead layer is a related issue for all ferroelectric materials we have neglected this effect in our simulations.…”

“…However, the industrial implementation of ferroelectric devices especially in nanoscale still missing due to the integration and scaling obstacles of conventionally used perovskite type ferroelectrics such as Lead Zirconate Titanate (PZT). The recently discovered ferroelectricity in HfO 2 thin films [6], enabled CMOS-compatible manufacturing of highly scaled ferroelectric devices down to 28 nm ground rule [6,7].…”

A thermally robust and thickness independent ferroelectric phase in laminated hafnium zirconium oxide

“…2 Primarily motivated by memory applications, thickness scaling to the single digit nanometer range, 3 3D-capacitor integration, 4 as well as ferroelectric field effect transistor implementation at the 28 nm node 5 has already been demonstrated. First results on non-memory applications of FE-HfO 2 such as negative capacitance FETs 6 or high energy storage capacitors using antiferroelectric hafnium oxide (AFE-HfO 2 ) 7 have already been reported.…”