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- 저자 : Venkateswarlu Gaddam (검색결과 2 건)
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A review on morphotropic phase boundary in fluorite-structure hafnia towards DRAM technology
Jung Minhyun,GADDAM VENKATESWARLU,전상훈 나노기술연구협의회 2022 Nano Convergence Vol.9 No.44
In the present hyper-scaling era, memory technology is advancing owing to the demand for high-performance computing and storage devices. As a result, continuous work on conventional semiconductor-process-compatible ferroelectric memory devices such as ferroelectric field-effect transistors, ferroelectric random-access memory, and dynamic random-access memory (DRAM) cell capacitors is ongoing. To operate high-performance computing devices, high-density, high-speed, and reliable memory devices such as DRAMs are required. Consequently, considerable attention has been devoted to the enhanced high dielectric constant and reduced equivalent oxide thickness (EOT) of DRAM cell capacitors. The advancement of ferroelectric hafnia has enabled the development of various devices, such as ferroelectric memories, piezoelectric sensors, and energy harvesters. Therefore, in this review, we focus the morphotropic phase boundary (MPB) between ferroelectric orthorhombic and tetragonal phases, where we can achieve a high dielectric constant and thereby reduce the EOT. We also present the role of the MPB in perovskite and fluorite structures as well as the history of the MPB phase. We also address the different approaches for achieving the MPB phase in a hafnia material system. Subsequently, we review the critical issues in DRAM technology using hafnia materials. Finally, we present various applications of the hafnia material system near the MPB, such as memory, sensors, and energy harvesters.
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Dipjyoti Das,Venkateswarlu Gaddam,Sanghun Jeon 대한전자공학회 2021 Journal of semiconductor technology and science Vol.21 No.1
In this paper, we investigate the ferroelectric properties of Al₂O₃/Hf0.5Zr0.5O₂ (HZO) dielectric/ferroelectric (DE/FE) bilayer stack for different DE layer thickness and annealing temperature. The DE/FE stack showed enhanced remanent polarization (Pr) as compared to the reference HZO capacitor for very thin DE layer due to the charge induced by the leakage current through the DE layer. On the contrary, for higher DE layer thickness, this charge injection is suppressed and the ferroelectricity in the DE/FE stack reduces due to the involvement of the depolarization field. An increase in the coercive field (Ec) of the DE/FE based capacitors was observed with increasing the DE layer thickness. Moreover, the Pr value of both HZO and DE/FE stack increases with increasing the annealing temperature till 800℃ and decrease thereafter. The addition of Al₂O₃ layer increases the thermal stability of the capacitors and despite the HZO capacitors being degraded at annealing temperature beyond 800℃, the DE/FE stack-based capacitors were found to demonstrate descent ferroelectricity.
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