Interfacial stress engineering toward enhancement of ferroelectricity in Al doped HfO₂ thin films

【摘要】 Ferroelectric HfO₂ has attracted much attention owing to its superior ferroelectricity at an ultra-thin thickness and good compatibility with Si-based complementary metal-oxide-semiconductor（CMOS） technology.However,the crystallization of polar orthorhombic phase（o-phase） HfO₂ is less competitive,which greatly limits the ferroelectricity of the as-obtained ferroelectric HfO₂ thin films.Fortunately,the crystallization of o-phase HfO₂ can be thermodynamically modulated via interfacial stress engineering.In this paper,the growth of improved ferroelectric Al doped HfO₂（HfO₂:Al）thin films on（111）-oriented Si substrate has been reported.Structural analysis has suggested that nonpolar monoclinic HfO₂:Al grown on（111）-oriented Si substrate suffered from a strong compressive strain,which promoted the crystallization of（111）-oriented o-phase HfO₂ in the as-grown HfO₂:Al thin films.In addition,the in-plane lattice of（111）-oriented Si substrate matches well with that of（111）-oriented o-phase HfO₂,which further thermally stabilizes the o-phase HfO₂.Accordingly,an improved ferroelectricity with a remnant polarization（2P_r） of 26.7 μC/cm² has been obtained.The results shown in this work provide a simple way toward the preparation of improved ferroelectric HfO₂ thin films.更多还原

【Abstract】 Ferroelectric HfO₂ has attracted much attention owing to its superior ferroelectricity at an ultra-thin thickness and good compatibility with Si-based complementary metal-oxide-semiconductor（CMOS） technology.However,the crystallization of polar orthorhombic phase（o-phase） HfO₂ is less competitive,which greatly limits the ferroelectricity of the as-obtained ferroelectric HfO₂ thin films.Fortunately,the crystallization of o-phase HfO₂ can be thermodynamically modulated via interfacial stress engineering.In this paper,the growth of improved ferroelectric Al doped HfO₂（HfO₂:Al）thin films on（111）-oriented Si substrate has been reported.Structural analysis has suggested that nonpolar monoclinic HfO₂:Al grown on（111）-oriented Si substrate suffered from a strong compressive strain,which promoted the crystallization of（111）-oriented o-phase HfO₂ in the as-grown HfO₂:Al thin films.In addition,the in-plane lattice of（111）-oriented Si substrate matches well with that of（111）-oriented o-phase HfO₂,which further thermally stabilizes the o-phase HfO₂.Accordingly,an improved ferroelectricity with a remnant polarization（2P_r） of 26.7 μC/cm² has been obtained.The results shown in this work provide a simple way toward the preparation of improved ferroelectric HfO₂ thin films.更多还原