Search

Flowchart illustrating how the films are deposited (a) without and (b) with cleaning step, and Auger electron spectroscopy depth profile of 15 nm HfNx deposited with precleaning step, before annealing (c) and after 900 °C annealing at NH3 atmosphere.

The chemical, physical, and electrical properties of the atomic layer deposited Hf0.5Zr0.5O2 thin films using tetrakis(ethylmethylamino) (TEMA) and tetrakis(dimethylamino) (TDMA) precursors are compared. The ligand of the metal-organic precursors strongly affects the residual C concentration, grain size, and the resulting ferroelectric properties. Depositing Hf0.5Zr0.5O2 films with the TDMA precursors results in lower C concentration and slightly larger grain size. These findings are beneficial to grow more ferroelectric-phase-dominant film, which mitigates its wake-up effect. From the wake-up test of the TDMA-Hf0.5Zr0.5O2 film with a 2.8 MV/cm cycling field, the adverse wake-up effect was well suppressed up to 105 cycles, with a reasonably high double remanent polarization value of ~40 μC/cm2. The film also showed reliable switching up to 109 cycles with the 2.5 MV/cm cycling field without involving the wake-up effect but with the typical fatigue behavior.

Charge injection from the near-by-electrode can occur during ferroelectric switching in the ferroelectric-dielectric bilayer due to the high field applied to the adjacent dielectric layers. The aim of this study is to investigate the effect of the charge injection by separating the amount of switched polarization and the injected charge density. A dynamic model of the injection-involved switching is developed and exploited to elucidate the mechanism. The model demonstrates that the amount of injected charges, which compensates for the bound charge of the polarization, can be larger, smaller, or identical to that of the polarization. This model further describes the analytical conditions of this compensation state. The model predictions are validated by the newly introduced ramping pulse measurements involving the serially connected TiN/Hf0.5Zr0.5O2/TiN and TiN/amorphous Al2O3/TiN, which are capable of separating the injected charge from the switched polarization. The dynamic model, along with the electrical measurements, enables the quantitative prediction and estimation of the internal potential and the effective charge, which is the sum of the bound and injected charges in the bilayer. This work provides fundamental insights into field-effect devices such as the next-generation ferroelectric-field-effect-transistors with NAND architecture based on uncompensated ferroelectric charges.

Interests in nanoscale integrated ferroelectric devices using doped HfO2-based thin films are actively reviving in academia and industry. The main driving force for the formation of the metastable non-centrosymmetric ferroelectric phase is considered to be the interface/grain boundary energy effect of the small grains in polycrystalline configuration. These small grains, however, can invoke unfavorable material properties, such as nonuniform switching performance. This study provides an in-depth understanding of such aspects of this material through careful measurement and modeling of the ferroelectric switching kinetics. Various previous switching models developed for conventional ferroelectric thin-film capacitors cannot fully account for the observed time- and voltage-dependent switching current evolution. The accurate fitting of the experimental results required careful consideration of the inhomogeneous field distribution across the electrode area, which could be acquired by an appropriate mathematic...

In this study, the influence of the HfOxNy interfacial layer (IL), interposed between the atomic layer deposited ferroelectric (FE) Hf0.5Zr0.5O2 thin film and TiN top electrode, on the FE properties of such a film was examined. The HfOxNy IL decreased the relative proportion of the non-FE monoclinic phase, possibly due to the N-doping effect. Furthermore, the oxidation of the TiN top electrode was also suppressed by the sacrificial oxidation of the HfOxNy IL during the rapid thermal process. As a result, the double remanent polarization of a Hf0.5Zr0.5O2 thin film could be enhanced from 40.2 to 48.2 μC/cm2 by the positive-up-negative-down test, and its degradation by fatigue during the endurance test can also be decreased. This result demonstrates the significance of interfacial engineering to optimize the FE properties of Hf0.5Zr0.5O2 films.

Ferroelectric (FE) capacitor is a critical electric component in microelectronic devices. Among many of its intriguing properties, the recent finding of voltage drop (V-drop) across the FE capacitor while the positive charges flow in is especially eye-catching. This finding was claimed to be direct evidence that the FE capacitor is in negative capacitance (NC) state, which must be useful for (infinitely) high capacitance and ultralow voltage operation of field-effect transistors. Nonetheless, the NC state corresponds to the maximum energy state of the FE material, so it has been widely accepted in the community that the material alleviates that state by forming ferroelectric domains. This work reports a similar V-drop effect from the 150 nm thick epitaxial BaTiO3 ferroelectric thin film, but the interpretation was completely disparate; the V-drop can be precisely simulated by the reverse domain nucleation and propagation of which charge effect cannot be fully compensated for by the supplied charge from th...

The chemical, physical, and electrical properties of the atomic layer deposited Hf0.5Zr0.5O2 thin films using tetrakis(ethylmethylamino) (TEMA) and tetrakis(dimethylamino) (TDMA) precursors are compared. The ligand of the metal-organic precursors strongly affects the residual C concentration, grain size, and the resulting ferroelectric properties. Depositing Hf0.5Zr0.5O2 films with the TDMA precursors results in lower C concentration and slightly larger grain size. These findings are beneficial to grow more ferroelectric-phase-dominant film, which mitigates its wake-up effect. From the wake-up test of the TDMA-Hf0.5Zr0.5O2 film with a 2.8 MV/cm cycling field, the adverse wake-up effect was well suppressed up to 105 cycles, with a reasonably high double remanent polarization value of ~40 μC/cm2. The film also showed reliable switching up to 109 cycles with the 2.5 MV/cm cycling field without involving the wake-up effect but with the typical fatigue behavior.

Ferroelectric Hf0.5Zr0.5O2 (HZO) films were grown by the atomic layer deposition (ALD) technique on an ALD or physical-vapor-deposited (PVD, sputtering) TiN bottom electrode (BE). The PVD TiN film showed small grains with flat surface morphology, mainly consisting of the (111) crystallographic plane. In contrast, the ALD TiN film exhibited a larger diameter and faceted grain shapes, with the (200) crystallographic surface planes. The 10-nm-thick HZO film on the ALD TiN BE showed a lower internal field, enhanced endurance (>1 × 1010 cycle at 2.5 MV/cm), and decreased leakage current than identical HZO films on the PVD TiN BE. Lower interfacial oxidation of the ALD TiN BE as a result of the smaller grain boundary area of the ALD TiN induced a lower defect density in the HZO film. The higher work function of the ALD TiN film also contributed to the lowering of the leakage current.

Interests in nanoscale integrated ferroelectric devices using doped HfO

M&S techniques are utilized for various purposes on the national defense, and its importance is increasing than ever. For analyzing RAM (Reliability, Availability and Maintainability) of weapon system, using M&S techniques can be more effective and practical way than deterministic approach, because M&S approach can consider uncertain variables and various constraints in the ILS (Integrated Logistics support) field. For design of ILS M&S, we first set up a purpose of M&S, attributes of real system and other similar ILS M&S tool. Then, we convert real system into model which consists of mathematical formula and logical expression. In this thesis, we introduce modeling procedures of M&S that describes total life cycle of ‘OO guided weapon system’ and the contents proposed in this paper can provide references for developing other M&S tool. Key words : RAM, ILS, M&S, DEVS, Guided weapon system요 약국방분야에서 M&S 기법은 분석, 훈련, 획득 등 다양한 목적으로 활용되고 있으며 그 중요성은 더욱 증가하고 있다 . 무기체계의 종합군수지원(ILS)요소 개발을 위한 RAM분석 시 M&S 기법을 활용하면 수리적인 기법만으로는 분석하기 어려운 시스템의 다양한 변수와 제약사항을 고려한 분석이 가능하다 . 무기체계의 RAM분석을 위한 ILS M&S도구를 설계하기 위해서는 M&S의 목적 설정, 무기체계의 특성 및 유사 M&S Tool 기능 분석 등의 활동이 선행되어야 하며 이를 바탕으로 실제 현실을 프로그램으로 구현하기 용이한 형태의 수학적, 논리적 언어로 모델링해야 한다. 본 논문에서는 ‘OO유도무기체계’의 배치부터 폐기 시까지 발생하는 운용 , 저장, 점검, 고장발생, 정비 등 제반 군수지원활동을 모의하여 유도무기체계의 수명주기 동안의 RAM 특성을 예측, 분석할 수 있는 M&S 도구의 모델링 과정을 제시하고자 하며 이는 유사 M&S 도구의 개발 시 참고자료로도 활용 가능할 것이다 .주요어 : RAM분석, 종합군수지원, 유도무기체계, 모델링, 시뮬레이션

Cemento-ossifying fibromas are benign tumors, and, although cases of an aggressive type have been reported, no cases of cemento-ossifying fibroma transforming into osteosarcoma have been documented previously. Low-grade osteosarcoma is a rare type of primary bone tumor, representing 1%-2% of all osteosarcomas. A 45-year-old female patient was diagnosed with cemento-ossifying fibroma, treated with mass excision several times over a period of two years and eight months, and followed up. After biopsy gathered because of signs of recurrence, she was diagnosed with low-grade osteosarcoma. The patient underwent wide excision, segmental mandibulectomy, and reconstruction with fibula free flap. The aim of this report is to raise awareness of the possibility that cemento-ossifying fibroma can transform into osteosarcoma and of the consequent necessity for careful diagnosis and treatment planning.

HfO

The negative capacitance (NC) effect in ferroelectric thin films has attracted a great deal of attention from the material and semiconductor device communities because it could be a possible solution to the impending problems related to field-effect transistor power consumption and dynamic random-access memory charge loss. A short discussion on the fundamental premise of the NC effect is presented. A phase-field model based on the time-dependent Ginzburg-Landau (TDGL) formalism in conjunction with the Chensky-Tarasenko (C-T) formalism for multidomain configuration is then developed to reveal the subtle correlation between the domain wall motion and NC effect for different thicknesses of ferroelectric and dielectric films. When a ferroelectric film becomes thin enough, a stripe domain structure can be achieved through competition between the electrostatic energy and domain wall energy. This stripe domain structure is quite resilient to transition to a homogeneous polarization state, making it very useful for (quasi-)static NC operation. Finally, the physical implications of the numerical results are explored with analytical modeling. It is identified that the domain wall motion in the stripe domain structure remains dominated by the external field, even when the entire film is in the (quasi-)static NC state.

Research of hafnium oxide-based ferroelectric materials has attracted much attention in the community with superior advantages of their compatibility with silicon. Also, negative capacitance (NC) effect from ferroelectric films attracts a great deal of attention because it could be one of the solutions for the high power-consumption issue of field effect transistors (FET). However, since the non-linear Q-V response of semiconductor in the FET structure in conjunction with the domain formation in the ferroelectric layer resulted in complicated device behaviors, it is necessary to understand the physics of the ferroelectric characteristics related to the interactions among the layers such as the depolarization field and charge trapping/injection for sub-60mV/dec subthreshold swing (SS) operation. In this study, the electrical properties of a Metal-Ferroelectric-Insulator-Semiconductor (MFIS) capacitor with a 7-10nm Hf0.5Zr0.5O2 (HZO) ferroelectric layer and an ultrathin interfacial oxide layer (SiO2) were examined in order to understand the underlying physics of the ferroelectric characteristics (Figure 1 (a)). These properties were compared with those of a Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) capacitor to analyze the interactions among each layer in the two different structures by pulse measurement. In addition, the ferroelectric characteristics of HZO on semiconductor related to the charge injection through the interfacial oxide layer with different thicknesses and the non-linear Q-V response of semiconductor have been investigated (Figure 1 (b)). Lastly, the effects of different PMA temperatures and HZO thicknesses were also examined and the experimental data were verified by the charge injection-controlled simulation model which was used to simulate the transfer characteristics based on different experimental conditions. (Figure 2). Figure 1

Warfighting experimentation is an important process for identifying requirements against changing military environment and for verifying proposed measures for reforming military service. The wargame simulation experiment is regarded as one of the most effective means to warfighting experimentation, and its importance is increasing than ever. On the other hand, the results of wargame experiments could be unreliable due to the uncertainty involved in the experimental procedure. To improve the reliability of the experimental results, systematic experimental procedures and analysis methods must be employed, and the design and analysis of experiments technique can be used effectively for this purpose. In this paper, AWAM, a wargame simulator, is used to optimize the organization of operational troops. The simulation model describes a warfighting situation in which the `survival rate of our force` and the `survival rate of the enemy force` are considered as responses, `the numbers of weapons in the squad` as control factors, and `the uncontrollable variables of the battlefield` as noise factors. In addition, for the purpose of effective experimentation, the product array approach in which the inner and outer orthogonal arrays are crossed is adopted. Then, the signal-to-noise-ratio for each response and the desirabilities for the means and standard deviations of responses are calculated and used to determine a compromise optimal solution. The experimental procedures and analysis methods developed in this paper can provide guidelines for designing and analyzing wargame simulation experiments for similar warfighting situations.

HfO2-ZrO2 solid-solution films were prepared by radio frequency sputtering, and the subsequent annealing process was optimized to render enhanced ferroelectric behavior. The target power, working pressure and O2 partial pressure ratios were varied, along with the annealing gas, time and temperature. Then, the film's structural and electrical properties were carefully scrutinized. Oxygen-deficient conditions were necessary during the sputter deposition to suppress grain growth, while annealing by O2 gas was critical to avoid defects and leakage problems. It is expected that the grain size difference under various deposition conditions combined with the degree of TiN top and bottom electrode oxidation by O2 gas will result in different ferroelectric behaviors. As a result, Hf0.5Zr0.5O2 prepared by radio frequency sputtering showed optimized ferroelectricity at 0% of O2 reactive gas, with a doubled remnant polarization value of ~20 μC cm−2 at a thickness of 11 nm. Film growth conditions with a high growth rate (4–5 nm min−1) were favorable for achieving the ferroelectric phase film, which feasibly suppressed both the grain growth and accompanying monoclinic phase formation.

We determine the anisotropy of the spin-fluctuation-induced pairing gap on the Fermi surface of the FeAs-based superconductors as function of the exchange and Hund's coupling ${J}_{H}$. We find that for sufficiently large ${J}_{H}$, nearly commensurate magnetic fluctuations yield a fully gapped ${s}^{\ifmmode\pm\else\textpm\fi{}}$-pairing state with small anisotropy of the gap amplitude on each Fermi-surface sheet, but significant variations of the gap amplitude for different sheets of the Fermi surface. In particular, we obtain the large variation of the gap amplitude on different Fermi-surface sheets, as seen in angular resolved photoemission spectroscopy experiments. For smaller values of Hund's coupling incommensurate magnetic fluctuations yield an ${s}^{\ifmmode\pm\else\textpm\fi{}}$-pairing state with line nodes. Such a state is also possible once the anisotropy of the material is reduced and three-dimensional effects come into play.

The reliability of flip chip solder joint is significantly affected by the property of surface finish. Various surface finishes such as ENIG, OSP, DIG, immersion Sn, and ENEPIG have been developed and widely used in the electronic packaging industry. Each surface finish has own advantages and disadvantages in terms of reliability and processing cost. ENIG has good diffusion barrier of Ni against solder and good wettability due to Au finish. However, brittle failure known as "black pad" has been issued as a potential reliability problem. In order to eliminate "black pad" failure, alternative Cu-based surface finishes such as OSP, DIG, and immersion Sn were suggested. However, these surface finishes also have reliability issues of rapid consumption of Cu and rapid growth of IMC. In this study, a surface finish was suggested with a concept of good diffusion barrier, which is advantage of ENIG, and good reliability without "black pad", which is advantage of Cu-based finishes. This surface finish, ENEC/OSP, is consisted of thick electroless Ni (/spl sim/ 6 /spl mu/m), thin electroless Cu (/spl sim/ 1 /spl mu/m), and OSP layer (/spl sim/ 0.3 /spl mu/m). In order to prevent the "black pad" failure caused by formation of P-rich Ni layer, thin electroless Cu layer was used as a sacrificial layer. After fabricating ENIG, ENEPIG, and ENEC/OSP finishes, interfacial reactions with Sn3.0Ag0.5Cu solder were investigated using SEM, EDX, EPMA, and TEM. In ENIG and ENEPIG, P-rich layer formed by Ni-Sn interfacial reaction was observed after solder reflow. Both ENIG and ENEPIG have potential risk of the "black pad" failure due to excessive P-rich layer growth. However, in ENEC/OSP, formation of P-rich layer was restricted by thin electroless Cu layer on electroless Ni-P layer. The sacrificial electroless Cu layer was not completely consumed after 1/spl times/ reflow. In addition, even after consumption of Cu layer in further reflow, thick Cu/sub 6/Sn/sub 5/ IMC layer also prevented diffusion of Sn and Ni, and therefore, the growth of P-rich layer was extremely limited. Thin electroless Cu layer which can restrict growth of P-rich layer should enhance the long-term reliability of solder joint without "black pad". Because of rapid Cu-Sn reaction rate, Cu/sub 6/Sn/sub 5/ IMC formed in ENEC/OSP finish had almost 3 times higher thickness than (Cu,Ni) /sub 6/Sn/sub 5/ IMC formed in ENIG and ENEPIG. (Cu,Ni) /sub 6/Sn/sub 5/ IMC observed in ENIG and ENEPIG was gradually growing with heat treatment, however, Cu/sub 6/Sn/sub 5/ IMC in ENEC/OSP was rapidly growing during initial reflow, then the growth rate of the IMC significantly reduced after consumption of the Cu layer. It means IMC thickness can be controlled by thickness of electroless Cu layer.