Optimization of performance and reliability of HZO-based capacitors for ferroelectric memory applications

In an era in which the amount of produced and stored data continues to exponentially grow, standard memory concepts start showing size, power consumption and costs limitation which make the search for alternative device concepts essential. Within a context where new technologies such as DRAM, magnetic RAM, resistive RAM, phase change memories and eFlash are explored and optimized, ferroelectric memory devices like FeRAM seem to showcase a whole range of properties which could satisfy market needs, offering the possibility of creating a non-volatile RAM. In fact, hafnia and zirconia-based ferroelectric materials opened up a new scenario in the memory technology scene, overcoming the dimension scaling limitations and the integration difficulties presented by their predecessors perovskite ferroelectrics. In particular, HfₓZr₁₋ₓO₂ stands out because of high processing flexibility and ease of integration in the standard semiconductor industry process flows for CMOS fabrication. Nonetheless, further understanding is necessary in order tocorrelate device performance and reliability to the establishment of ferroelectricity itself. The aim of this work is to investigate how the composition of the ferroelectric oxide, together with the one of the electrode materials influence the behavior of a ferroelectric RAM. With this goal, different process parameters and reliability properties are considered and an analysis of the polarization reversal is performed. Starting from undoped hafnia and zirconia and subsequently examining their intermixed system, it is shown how surface/volume energy contributions, mechanical stress and oxygen-related defects all concur in the formation of the ferroelectric phase. Based on the process optimization of an HfₓZr₁₋ₓO₂-based capacitor performed within these pages, a 64 kbit 1T1C FeRAM array is demonstrated by Sony Semiconductor Solutions Corporation which shows write voltage and latency as low as 2.0 V and 16 ns, respectively. Outstanding retention and endurance performances are also predicted, which make the addressed device an extremely strong competitor in the semiconductor scene

Recent progress for obtaining the ferroelectric phase in hafnium oxide based films: impact of oxygen and zirconium

Different causes for ferroelectric properties in hafnium oxide were discussed during the last decade including various dopants, stress, electrode materials, and surface energy from different grain sizes. Recently, the focus shifted to the impact of oxygen vacancies on the phase formation process. In this progress report, the recent understanding of the influence of oxygen supplied during deposition on the structural phase formation process is reviewed and supplemented with new data for mixed HfₓZr₁₋ₓOᵧ films. Even though polar and non-polar HfₓZr₁₋ₓOᵧ thin films are well characterized, little is known about the impact of oxygen exposure during the deposition process. Here, a combination of structural and electrical characterization is applied to investigate the influence of the oxygen and zirconium content on the crystallization process during ALD deposition in comparison to other deposition techniques. Different polarization properties are assessed which correlate to the determined phase of the film. Optimized oxygen pulse times can enable the crystallization of HfₓZr₁₋ₓOᵧ in a polar orthorhombic phase rather than a non-polar monoclinic and tetragonal phase

The Electrode-Ferroelectric Interface as the Primary Constraint on Endurance and Retention in HZO-Based Ferroelectric Capacitors

Ferroelectric hafnium-zirconium oxide is one of the most relevant CMOS-compatible materials for next-generation, non-volatile memory devices. Nevertheless, performance reliability remains an issue. With TiN electrodes (the most reported electrode material), Hf-Zr-based ferroelectric capacitors struggle to provide reliable retention due to electrode-ferroelectric interface interactions. Although Hf-Zr-based ferroelectric capacitors are fabricated with other electrodes, the focus is predominantly directed toward obtaining a large ferroelectric response. The impact of the electrodes on data retention for these ferroelectrics remains underreported and greater insight is needed to improve device reliability. Here, a comprehensive set of electrodes are evaluated with emphasis on the core ferroelectric memory reliability metrics of endurance, retention, and imprint. Metal-ferroelectric-metal capacitors comprised of a Hf0.5Zr0.5O2 layer deposited between different combinations of nitride (TiN, TiAlN, and NbN), pure metal (W), and oxide (MoO2, RuO2, and IrO2) top and bottom electrodes are fabricated for the investigation. From the electrical, physical, and structural analysis, the low reactivity of the electrode with the ferroelectric is found to be key for improved reliability of the ferroelectric capacitor. This understanding of interface properties provides necessary insight for the broad implementation of Hf-Zr-based ferroelectrics in memory technology and, overall, boosts the development of next-generation memories

Optimization of performance and reliability of HZO-based capacitors for ferroelectric memory applications

In an era in which the amount of produced and stored data continues to exponentially grow, standard memory concepts start showing size, power consumption and costs limitation which make the search for alternative device concepts essential. Within a context where new technologies such as DRAM, magnetic RAM, resistive RAM, phase change memories and eFlash are explored and optimized, ferroelectric memory devices like FeRAM seem to showcase a whole range of properties which could satisfy market needs, offering the possibility of creating a non-volatile RAM. In fact, hafnia and zirconia-based ferroelectric materials opened up a new scenario in the memory technology scene, overcoming the dimension scaling limitations and the integration difficulties presented by their predecessors perovskite ferroelectrics. In particular, HfₓZr₁₋ₓO₂ stands out because of high processing flexibility and ease of integration in the standard semiconductor industry process flows for CMOS fabrication. Nonetheless, further understanding is necessary in order tocorrelate device performance and reliability to the establishment of ferroelectricity itself. The aim of this work is to investigate how the composition of the ferroelectric oxide, together with the one of the electrode materials influence the behavior of a ferroelectric RAM. With this goal, different process parameters and reliability properties are considered and an analysis of the polarization reversal is performed. Starting from undoped hafnia and zirconia and subsequently examining their intermixed system, it is shown how surface/volume energy contributions, mechanical stress and oxygen-related defects all concur in the formation of the ferroelectric phase. Based on the process optimization of an HfₓZr₁₋ₓO₂-based capacitor performed within these pages, a 64 kbit 1T1C FeRAM array is demonstrated by Sony Semiconductor Solutions Corporation which shows write voltage and latency as low as 2.0 V and 16 ns, respectively. Outstanding retention and endurance performances are also predicted, which make the addressed device an extremely strong competitor in the semiconductor scene

Optimization of performance and reliability of HZO-based capacitors for ferroelectric memory applications

In an era in which the amount of produced and stored data continues to exponentially grow, standard memory concepts start showing size, power consumption and costs limitation which make the search for alternative device concepts essential. Within a context where new technologies such as DRAM, magnetic RAM, resistive RAM, phase change memories and eFlash are explored and optimized, ferroelectric memory devices like FeRAM seem to showcase a whole range of properties which could satisfy market needs, offering the possibility of creating a non-volatile RAM. In fact, hafnia and zirconia-based ferroelectric materials opened up a new scenario in the memory technology scene, overcoming the dimension scaling limitations and the integration difficulties presented by their predecessors perovskite ferroelectrics. In particular, HfₓZr₁₋ₓO₂ stands out because of high processing flexibility and ease of integration in the standard semiconductor industry process flows for CMOS fabrication. Nonetheless, further understanding is necessary in order tocorrelate device performance and reliability to the establishment of ferroelectricity itself. The aim of this work is to investigate how the composition of the ferroelectric oxide, together with the one of the electrode materials influence the behavior of a ferroelectric RAM. With this goal, different process parameters and reliability properties are considered and an analysis of the polarization reversal is performed. Starting from undoped hafnia and zirconia and subsequently examining their intermixed system, it is shown how surface/volume energy contributions, mechanical stress and oxygen-related defects all concur in the formation of the ferroelectric phase. Based on the process optimization of an HfₓZr₁₋ₓO₂-based capacitor performed within these pages, a 64 kbit 1T1C FeRAM array is demonstrated by Sony Semiconductor Solutions Corporation which shows write voltage and latency as low as 2.0 V and 16 ns, respectively. Outstanding retention and endurance performances are also predicted, which make the addressed device an extremely strong competitor in the semiconductor scene

Impact of vacancies and impurities on ferroelectricity in PVD- and ALD-grown HfO2_2 films

We investigate the emerging chemical states of TiN/HfO$_2$/TiN capacitors and focus especially on the identification of vacancies and impurities in the ferroelectric HfO$_2$ layers, which are produced either by physical vapor deposition (PVD) or atomic layer deposition (ALD). Depending on the specific growth conditions, we identify different mechanisms of oxygen vacancy formation. Corresponding spectral features are consistently observed for all HfO$_2$- and TiN-related core levels by hard x-ray photoelectron spectroscopy (HAXPES). In ALD-grown samples, we find spectral signatures for the electronic interaction between oxygen vacancies and nitrogen impurities. By linking the HAXPES results to electric field cycling experiments on the TiN/HfO$_2$/TiN capacitors, we discuss possible formation mechanisms and stabilization of the ferroelectric HfO$_2$ phase directly related to specific PVD or ALD conditions

Material perspectives of HfO₂-based ferroelectric films for device applications

Ferroelectric HfO₂ attracts a huge amount of attention not only for memory and negative capacitance, but also for programmable logic including memory-in-logic and neuromorphic applications. However, the understanding of material fundamentals still needs to be improved. This paper gives material fundamentals and new insights to this ferroelectric material for future device applications. In particular, the key role of dopants, effects of the interface on the ferroelectric phase, and a detailed discussion of the switching kinetics are of central focus. Based on material properties newly obtained, we discuss opportunities of ferroelectric HfO₂ for device applications

The Electrode‐Ferroelectric Interface as the Primary Constraint on Endurance and Retention in HZO‐Based Ferroelectric Capacitors

International audienceAbstract Ferroelectric hafnium‐zirconium oxide is one of the most relevant CMOS‐compatible materials for next‐generation, non‐volatile memory devices. Nevertheless, performance reliability remains an issue. With TiN electrodes (the most reported electrode material), Hf‐Zr‐based ferroelectric capacitors struggle to provide reliable retention due to electrode‐ferroelectric interface interactions. Although Hf‐Zr‐based ferroelectric capacitors are fabricated with other electrodes, the focus is predominantly directed toward obtaining a large ferroelectric response. The impact of the electrodes on data retention for these ferroelectrics remains underreported and greater insight is needed to improve device reliability. Here, a comprehensive set of electrodes are evaluated with emphasis on the core ferroelectric memory reliability metrics of endurance, retention, and imprint. Metal‐ferroelectric‐metal capacitors comprised of a Hf 0.5 Zr 0.5 O 2 layer deposited between different combinations of nitride (TiN, TiAlN, and NbN), pure metal (W), and oxide (MoO 2 , RuO 2 , and IrO 2 ) top and bottom electrodes are fabricated for the investigation. From the electrical, physical, and structural analysis, the low reactivity of the electrode with the ferroelectric is found to be key for improved reliability of the ferroelectric capacitor. This understanding of interface properties provides necessary insight for the broad implementation of Hf‐Zr‐based ferroelectrics in memory technology and, overall, boosts the development of next‐generation memories

Origin of Ferroelectric Phase in Undoped HfO2 Films Deposited by Sputtering

Thin film metal–insulator–metal capacitors with undoped HfO2 as the insulator are fabricated by sputtering from ceramic targets and subsequently annealed. The influence of film thickness and annealing temperature is characterized by electrical and structural methods. After annealing, the films show distinct ferroelectric properties. Grazing incidence X-ray diffraction measurements reveal a dominant ferroelectric orthorhombic phase for thicknesses in the 10–50 nm range and a negligible non-ferroelectric monoclinic phase fraction. Sputtering HfO2 with additional oxygen during the deposition decreases the remanent polarization. Overall, the impact of oxygen vacancies and interstitials in the HfO2 film during deposition and annealing is correlated to the phase formation process. © 2019 WILEY-VCH Verlag GmbH & Co. KGaA, WeinheimN

Origin of Ferroelectric Phase in Undoped HfO2_{2} Films Deposited by Sputtering

Thin film metal–insulator–metal capacitors with undoped HfO$_2$ as the insulator are fabricated by sputtering from ceramic targets and subsequently annealed. The influence of film thickness and annealing temperature is characterized by electrical and structural methods. After annealing, the films show distinct ferroelectric properties. Grazing incidence X‐ray diffraction measurements reveal a dominant ferroelectric orthorhombic phase for thicknesses in the 10–50 nm range and a negligible non‐ferroelectric monoclinic phase fraction. Sputtering HfO$_2$ with additional oxygen during the deposition decreases the remanent polarization. Overall, the impact of oxygen vacancies and interstitials in the HfO$_2$ film during deposition and annealing is correlated to the phase formation process