Seungyeol Oh
포항공과대학교 공과대학 전기공학과 · 공학
이 교수의 연구실은 허프지르옥사이드(HfZrO₂, HZO) 기반 페로일렉트릭 소재를 중심으로, 신경형 컴퓨팅과 메모리 장치에 응용 가능한 다중 수준의 비휘류성 전극 특성을 연구하고 있습니다. 특히, 페로일렉트릭 필드효과트랜지스터와 신경망 시뮬레이션을 통해 인공 시냅스 기반 하드웨어 신경망의 구현 가능성을 탐색하고 있으며, 고성능 및 내구성 향상을 위한 공정 최적화와 인터페이스 제어 기술도 핵심 과제입니다. 또한, HZO의 상전이 특성과 고체상 구조 제어를 통해 DRAM 및 고k 절연막 응용까지 확장하고 있습니다.
표시된 성과는 수집된 데이터 기준으로 산출되며, 일부 차이가 있을 수 있습니다.
We propose a HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> (HZO)-based ferroelectric synapse device with multi-levels states of remnant polarization that is equivalent to multi-levels conductance states. By optimizing the pulse condition, we obtained 32 levels of remnant polarization states for both potentiation and depression. Furthermore, a ferroelectric field-effect transistor is simulated using the obtained multiple remnan
Ferroelectric materials are promising candidates for synaptic weight elements in neural network hardware because of their nonvolatile multilevel memory effect. This feature is crucial for their use in mobile applications such as inference when vector matrix multiplication is performed during portable artificial intelligence service. In addition, the adaptive learning effect in ferroelectric polarization has gained considerable research attention for reducing the CMOS circuit overhead of an integ
In this study, we investigate the effects of various electrodes on the ferroelectric properties of ultrathin HfZrOx (HZO) films. The ferroelectric polarization is totally suppressed in the HZO films with TiN and W bottom electrodes when the film thickness is below 5 nm. These results can be attributed to the formation of a dead layer at the bottom electrode/HZO interface during the atomic layer deposition (ALD) and annealing processes. On the other hand, the HZO film with a Pt bottom electrode s
We investigate the effects of high-pressure hydrogen annealing (HPHA) on W/ferroelectric Al:HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /interface layer (IL)/Si stacks. With HPHA, degradation in remnant polarization is observed in the pristine state due to ferroelectric domain pinning. However, after wake-up, a comparable remnant polarization is observed by domain de-pinning. In addition, HPHA improves the quality current and low int
This study evaluates HfxZr1-xO2 (HZO)-based high-k dielectrics, where dielectric constant (k) is significantly enhanced through structural engineering. The investigation focuses on their dielectric characteristics by pulse operation for DRAM applications. HZO/ZrO2 (HZZ) films with different superlattice structures display different dielectric behaviors, including ferroelectricity, morphotropic phase boundary (MPB), and anti-ferroelectricity. The HZZ film at the MPB condition exhibits exceptional
HfxZr1-xO2 thin films exhibit a high dielectric constant at the morphotropic phase boundary (MPB), which is beneficial for high-k dielectric applications. To minimize the equivalent oxide thickness, the effects of various HZO thicknesses and compositions on the MPB were investigated. In general, HZO films with a thickness of 10 nm exhibit a high dielectric constant owing to MPB at a composition of Hf:Zr = 3:7. However, it was confirmed that composition optimization is required for HZO films with
Abstract With the increasing demand for high‐performance computing and storage solutions, industries are under pressure to deliver enhanced‐density, high‐speed, cost‐efficient, and reliable memory technologies. The development of advanced high dielectric constant (high‐k) dielectrics for dynamic random‐access memory (DRAM) remains essential yet challenging, with a need for further advancements on scaling and mass production compatibility. A significant advancement has been the discovery of morph
To improve the turn-off speed and uniformity of atomic threshold switching (TS) devices, we propose the use of the AgSe electrode and controlled bipolar pulse forming method. Compared with TS devices with Ag and AgTe electrodes, TS device with the AgSe electrode shows an extremely fast turn-off speed, which can be explained by the limited injection of Ag into the switching layer. By applying positive bias (Icc=500 nA, 1 ms) followed by negative bias (-0.1 to -0.2 V, 10 μs), the TS device exhibit
It is important to obtain ferroelectric HfZrO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</inf> (HZO) films at low crystallization temperatures to ensure compatibility with low-temperature processes. This study investigates the origin of degradation in ferroelectric properties of ferroelectric films at low crystallization temperatures, by modifying the bottom electrodes and HZO thicknesses. The TiN/HZO/TiN and W/HZO/W stacks exhibit no or very
