Hf_(0.5)Zr_(0.5)O_(2)(HZO)ferroelectric thin films have gained significant attention for the development of next-generation ferroelectric memories by complementary-metal-oxide semiconductor(CMOS)back-end-of-line(BEOL)...Hf_(0.5)Zr_(0.5)O_(2)(HZO)ferroelectric thin films have gained significant attention for the development of next-generation ferroelectric memories by complementary-metal-oxide semiconductor(CMOS)back-end-of-line(BEOL)processing,due to their relatively low crystallization temperature.However,it remains challenging to achieve excellent ferroelectric properties with post deposition annealing(PDA)process at a BEOL compatible temperature.Along these lines,in this work,it is demonstrated that the ferroelec-tricity of 15 nm thick HZO thin film prepared by PDA process at 400℃can be improved to varying degrees,via depositing 2 nm thick dielectric layers of Al_(2)O_(3),HfO_(2),or ZrO_(2)at either the bottom or the top of the film.Notably,the HZO thin film with the top-Al_(2)O_(3)layer exhibits remarkable ferroelectric prop-erties,which are independent of the thickness of HZO.The 6 nm thick HZO thin film shows a total remanent polarization(2Pr)of 31 mC/cm^(2)under an operating voltage of 2.5 V.These results represent a significant advancement in the fabrication of high-performance,BEOL compatible ferroelectric mem-ories,as compared to previously reported state-of-the-art works.展开更多
The rapid development of 5G,big data,and Internet of Things(IoT)technologies is urgently required for novel non-volatile memory devices with low power consumption,fast read/write speed,and high reliability,which are c...The rapid development of 5G,big data,and Internet of Things(IoT)technologies is urgently required for novel non-volatile memory devices with low power consumption,fast read/write speed,and high reliability,which are crucial for high-performance computing.Ferroelectric memory has undergone extensive investigation as a viable alternative for commercial applications since the post-Moore era.However,conventional perovskite-structure ferroelectrics(e.g.,PbZr_(x)Ti_(1-x)O_(3))encounter severe limitations for high-density integration owing to the size effect of ferroelectricity and incompatibility with complementary metal-oxide-semiconductor technology.Since 2011,the ferroelectric field has been primarily focused on HfO_(2)-based ferroelectric thin films owing to their exceptional scalability.Several reviews discussing the control of ferroelectricity and device applications exist.It is believed that a comprehensive understanding of mechanisms based on industrial requirements and concerns is necessary,such as the wake-up effect and fatigue mechanism.These mechanisms reflect the atomic structures of the materials as well as the device physics.Herein,a review focusing on phase stability and domain structure is presented.In addition,the recent progress in related ferroelectric memory devices and their challenges is briefly discussed.展开更多
HfO_(2)-based ferroelectrics have evoked considerable interest owing to the complementary metal-oxide semiconductor compatibility and robust ferroelectricity down to a few unit cells.However,the unique wake-up effect ...HfO_(2)-based ferroelectrics have evoked considerable interest owing to the complementary metal-oxide semiconductor compatibility and robust ferroelectricity down to a few unit cells.However,the unique wake-up effect of HfO_(2)-based ferroelectric films severely restricts the improvement of their performance.In particular,the domain structure is an important characteristic of ferroelectric materials,which still has not been well understood in HfO_(2)-based ferroelectrics.In this work,a Hf_(0.5)Zr_(0.5)O_(2) ferroelectric thin film is grown on a typical Si substrate buffered with TiN electrode.The 90°domains of the Pca21 ferroelectric phase with head-to-tail and tail-to-tail structures can be observed by Cs-corrected scanning transmission electron microscope under their pristine condition.After waking up,the 180°domain is displayed in the ferroelectric phase.The remarkable differences in domain walls for 90°and 180°domains are characterized by qualitatively mapping the polarization distributions at the atomic scale.The domain wall changes from the[101]of the Hf_(0.5)Zr_(0.5)O_(2) film to the[001]of the Hf_(0.5)Zr_(0.5)O_(2) film.This result provides fundamental information for understanding the domain structure of HfO_(2)-based ferroelectrics.展开更多
Multilevel ferroelectric field-effect transistors(FeFETs)integrated with HfO_(2)-based ferroelectric thin films demonstrate tremendous potential in high-speed massive data storage and neuromorphic computing applicatio...Multilevel ferroelectric field-effect transistors(FeFETs)integrated with HfO_(2)-based ferroelectric thin films demonstrate tremendous potential in high-speed massive data storage and neuromorphic computing applications.However,few works have focused on the stability of the multiple memory states in the HfO_(2)-based FeFETs.Here we firstly report the write/read disturb effects on the multiple memory states in the Hf_(0.5)Zr_(0.5)O_(2)(HZO)-based FeFETs.The multiple memory states in HZO-based FeFETs do not show obvious degradation with the write and read disturb cycles.Moreover,the retention characteristics of the intermediate memory states in HZO-based FeFETs with unsaturated ferroelectric polarizations are better than that of the memory state with saturated ferroelectric polarization.Through the deep analysis of the operation principle of in HZO-based FeFETs,we speculate that the better retention properties of intermediate memory states are determined by the less ferroelectric polarization degradation and the weaker ferroelectric polarization shielding.The experimental and theoretical evidences confirm that the long-term stability of the intermediate memory states in HZO-based FeFETs are as robust as that of the saturated memory state,laying a solid foundation for their practical applications.展开更多
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.52122205,52102147,52072324,11932016)the China Postdoctoral Science Foundation(2022M712674).
文摘Hf_(0.5)Zr_(0.5)O_(2)(HZO)ferroelectric thin films have gained significant attention for the development of next-generation ferroelectric memories by complementary-metal-oxide semiconductor(CMOS)back-end-of-line(BEOL)processing,due to their relatively low crystallization temperature.However,it remains challenging to achieve excellent ferroelectric properties with post deposition annealing(PDA)process at a BEOL compatible temperature.Along these lines,in this work,it is demonstrated that the ferroelec-tricity of 15 nm thick HZO thin film prepared by PDA process at 400℃can be improved to varying degrees,via depositing 2 nm thick dielectric layers of Al_(2)O_(3),HfO_(2),or ZrO_(2)at either the bottom or the top of the film.Notably,the HZO thin film with the top-Al_(2)O_(3)layer exhibits remarkable ferroelectric prop-erties,which are independent of the thickness of HZO.The 6 nm thick HZO thin film shows a total remanent polarization(2Pr)of 31 mC/cm^(2)under an operating voltage of 2.5 V.These results represent a significant advancement in the fabrication of high-performance,BEOL compatible ferroelectric mem-ories,as compared to previously reported state-of-the-art works.
基金the National Natural Science Foundation of China(11932016,52122205,and 52072324)for their financial support of this work.
文摘The rapid development of 5G,big data,and Internet of Things(IoT)technologies is urgently required for novel non-volatile memory devices with low power consumption,fast read/write speed,and high reliability,which are crucial for high-performance computing.Ferroelectric memory has undergone extensive investigation as a viable alternative for commercial applications since the post-Moore era.However,conventional perovskite-structure ferroelectrics(e.g.,PbZr_(x)Ti_(1-x)O_(3))encounter severe limitations for high-density integration owing to the size effect of ferroelectricity and incompatibility with complementary metal-oxide-semiconductor technology.Since 2011,the ferroelectric field has been primarily focused on HfO_(2)-based ferroelectric thin films owing to their exceptional scalability.Several reviews discussing the control of ferroelectricity and device applications exist.It is believed that a comprehensive understanding of mechanisms based on industrial requirements and concerns is necessary,such as the wake-up effect and fatigue mechanism.These mechanisms reflect the atomic structures of the materials as well as the device physics.Herein,a review focusing on phase stability and domain structure is presented.In addition,the recent progress in related ferroelectric memory devices and their challenges is briefly discussed.
基金This work is supported by the National Natural Science Foundation of China(nos.51901166,11932016,52122205,52072400,and 52025025)the Fundamental Research Funds for the Central Universities(no.QTZX22064).
文摘HfO_(2)-based ferroelectrics have evoked considerable interest owing to the complementary metal-oxide semiconductor compatibility and robust ferroelectricity down to a few unit cells.However,the unique wake-up effect of HfO_(2)-based ferroelectric films severely restricts the improvement of their performance.In particular,the domain structure is an important characteristic of ferroelectric materials,which still has not been well understood in HfO_(2)-based ferroelectrics.In this work,a Hf_(0.5)Zr_(0.5)O_(2) ferroelectric thin film is grown on a typical Si substrate buffered with TiN electrode.The 90°domains of the Pca21 ferroelectric phase with head-to-tail and tail-to-tail structures can be observed by Cs-corrected scanning transmission electron microscope under their pristine condition.After waking up,the 180°domain is displayed in the ferroelectric phase.The remarkable differences in domain walls for 90°and 180°domains are characterized by qualitatively mapping the polarization distributions at the atomic scale.The domain wall changes from the[101]of the Hf_(0.5)Zr_(0.5)O_(2) film to the[001]of the Hf_(0.5)Zr_(0.5)O_(2) film.This result provides fundamental information for understanding the domain structure of HfO_(2)-based ferroelectrics.
基金This work was partly supported by the National Natural Science Foundation of China(Grant Nos.52122205,51902274,52072324,and 11932016)the Science and Technology Innovation Program of Hunan Province(Grant No.2020RC2077)the Natural Science Foundation of Hunan Province(Grant No.2019JJ50617).
文摘Multilevel ferroelectric field-effect transistors(FeFETs)integrated with HfO_(2)-based ferroelectric thin films demonstrate tremendous potential in high-speed massive data storage and neuromorphic computing applications.However,few works have focused on the stability of the multiple memory states in the HfO_(2)-based FeFETs.Here we firstly report the write/read disturb effects on the multiple memory states in the Hf_(0.5)Zr_(0.5)O_(2)(HZO)-based FeFETs.The multiple memory states in HZO-based FeFETs do not show obvious degradation with the write and read disturb cycles.Moreover,the retention characteristics of the intermediate memory states in HZO-based FeFETs with unsaturated ferroelectric polarizations are better than that of the memory state with saturated ferroelectric polarization.Through the deep analysis of the operation principle of in HZO-based FeFETs,we speculate that the better retention properties of intermediate memory states are determined by the less ferroelectric polarization degradation and the weaker ferroelectric polarization shielding.The experimental and theoretical evidences confirm that the long-term stability of the intermediate memory states in HZO-based FeFETs are as robust as that of the saturated memory state,laying a solid foundation for their practical applications.
