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Electron beam induced current (EBIC) method is employed to analyze gettered Czochralski silicon. The effect of three different sequences of thermal treatments applied in ultralarge scale integration device manufacturing, both on the denuded zone (DZ) and intrinsic site formation, is assessed. EBIC method offers essential and direct data on DZ thickness and thorough homogeneity as well as on minority carrier diffusion length degradation in silicon substrates. The results are discussed.

Atomic defects in high-k materials affect the performance, reliability, variability, and scaling potential of electronic devices. Their characterization is thus of paramount importance, and methods exploiting electrical measurements are highly demanded. In this work we present a novel method for extracting the defect properties from I-V curve hysteresis measured at low electric field in thick metal-insulator-metal (MIM) stacks. The I-V curve hysteresis allows detecting the defects located near the electrode-insulator interfaces and aligned with the stack Fermi level, and extracting their properties. The defects are profiled cross-correlating the information provided by the low-field current hysteresis and the high-field steady-state current. This technique can be applied to MIM stacks fabricated in Back-End-of-Line for capacitors, embedded memories and thin film transistors. [ABSTRACT FROM AUTHOR]

Resistive switching in binary metal oxides consists of conductivity changes originating from the electrical creation/dissolution of conductive filaments (CFs) at nanoscale. The investigation of CF local properties can only be achieved through physical and electrical studies at the scale of 10 nm or less, that is, the characteristic size of CFs. This work reports on the direct manipulation of individual CFs formed through insulating NiO films by conductive atomic force microscopy (CAFM) and the comparison between forming/reset processes induced by CAFM and those observed in large-area devices with the same NiO film. The switching variability due to local defects, such as grain boundaries and dislocations, is directly evidenced by CAFM during electroforming process. Our results also indicate that the forming voltage under CAFM can be significantly smaller than the one observed in large-area devices, thus providing evidence for the electric-field enhancement underneath the CAFM tip. Filament deactivation, or reset, at extremely low currents close to 100 nA is demonstrated and described in terms of electrode-limited CF. These results suggest that device engineering and CF size limitation may allow for a significant reduction of forming voltage and reset current in resistive switching random-access memory switching. [ABSTRACT FROM AUTHOR]

Resistive switching memory (RRAM) based on the redox-induced conductivity change in some metal oxides attracts considerable interest as a new technology for next-generation nonvolatile electronic storage. Although resistance-switching phenomena in several transition metal oxides have been known from decades, the details of the switching mechanisms and the nature of the different resistive states are still largely debated. For nonvolatile memory applications, the scaling potential of RRAMs is the most relevant issue, and understanding the scaling capability of RRAM devices requires a sound interpretation of resistance-switching operation and reliability aspects. This work addresses the scaling dependence of RRAM switching parameters. The dependence on the electrode area and on the size of the conductive filament (CF) responsible for low-resistance memory state is investigated. The RRAM conduction modes depending on CF size are discussed based on temperature dependent resistance analysis. Reset characteristics in different resistance states are explained by a Joule heating model for CF oxidation. [ABSTRACT FROM AUTHOR]

The morphological and electrical evolution of HfO2 and ZrO2 thin films is investigated on the nanoscale using conducting atomic-force microscopy in ultrahigh vacuum. Films of different thicknesses have been grown by atomic layer deposition. With increasing film thickness the film structure changes from amorphous to polycrystalline. By conducting atomic-force microscopy using local current–voltage curve statistics and two-dimensional current imaging it is found that the formation of crystallites has different effects on the electrical properties of the two dielectrics. In the case of HfO2, the crystalline fraction causes weak spots in the oxide, whereas for the ZrO2 films the crystallites exhibit lower leakage currents compared to the amorphous matrix and leakage is mainly determined by thickness fluctuations. [ABSTRACT FROM AUTHOR]

The morphological and electrical evolution of HfO2 and ZrO2 thin films is investigated on the nanoscale using conducting atomic-force microscopy in ultrahigh vacuum. The formation of crystallites having different effects on the electrical properties of two dielectrics is observed by conducting atomic-force microscopy using local current-voltage curve statistics and two-dimensional current imaging.

The resistance switching dynamics of TiN/HfO2/Pt devices is analyzed in this paper. When biased with a voltage ramp of appropriate polarity, the devices experience SET transitions from high to low resistance states in an abrupt manner, which allows identifying a threshold voltage. However, we find that the stimulation with trains of identical pulses at voltages near the threshold results in a gradual SET transition, whereby the resistive state visits a continuum of intermediate levels as it approaches some low resistance state limit. On the contrary, RESET transitions from low to high resistance states proceed in a gradual way under voltage ramp stimulation, while gradual resistance changes driven by trains of identical spikes cover only a limited resistance window. The results are discussed in terms of the relations among the thermo-electrochemical effects of Joule heating, ion mobility, and resistance change, which provide positive and negative closed loop processes in SET and RESET, respectively. Furthermore, the effect of the competition between opposite tendencies of filament dissolution and formation at opposite metal/HfO2 interfaces is discussed as an additional ingredient affecting the switching dynamics. [ABSTRACT FROM AUTHOR]

The multiple resistive switching of Pt/HfO2/TiN devices is demonstrated as a result of a competition between the switching at opposite metal/oxide interfaces. Three switching operation modes are demonstrated: clockwise (CW) switching (set for negative voltage and reset for positive voltage at Pt electrode), as already reported in literature for similar material stacks; counterclockwise (CCW) switching and complementary switching (CS) that consist in a set and a reset for increasing voltage of the same polarity. The multiple switching operation modes are enabled by a deep-reset operation that brings the cell resistance close to the initial one. As a consequence, the set transition after a deep-reset occurs at the same voltage and currents as those of the forming and leads to a low resistance state whose resistance can be further decreased in a CCW switching or increased back with a CW switching. With a suitable choice of the stop voltage, a CS in obtained, as well. The coexistence of all three CW, CCW, and CS operations demonstrates that both metal-oxide interfaces are active in the formation and the dissolution of conductive filaments responsible for the switching. All these observations are discussed in terms of a competition between ion migration processes occurring at the opposite metal-oxide interfaces. [ABSTRACT FROM AUTHOR]

Data centre optical links are migrating to four‐level pulse amplitude modulation (PAM‐4) as a method to extend the data rate while covering longer distances. Vertical‐cavity surface‐emitting lasers (VCSELs) enable the integration of low‐power transmitters, but their non‐linear and bias‐dependent behaviour makes conventional feed‐forward equalisation less effective. This Letter presents a 0.13μm SiGe BiCMOS PAM‐4 driver that boosts the falling‐edge to the bottom level through a selective pre‐emphasis technique. Experiments at 25 GBd (50 Gb/s) reveal that adding selective pre‐emphasis to a 4‐tap equalised current driving a 20.6 GHz 1.5μm VCSEL, relaxes the critical PAM‐4 link budget requirements by >1 dB at the KP4 forward error correction threshold of 2.2×10−4. The potential of PAM‐4 VCSEL transmitters can be significantly enhanced by including selective pre‐emphasis to the equalisation topology while requiring minimal overhead. [ABSTRACT FROM AUTHOR]

Magnesium oxide (MgO) films have been grown by atomic layer deposition in the wide deposition temperature window of 80–350 °C by using bis(cyclopentadienyl)magnesium and H2O precursors. MgO thin films are deposited on both HF-last Si(1 0 0) and SiO2/Si substrates at a constant growth rate of ∼0.12 nm cycle−1. The structural, morphological and chemical properties of the synthesized MgO thin films are investigated by x-ray reflectivity, grazing incidence x-ray diffraction, time-of-flight secondary ion mass spectrometry and atomic force microscopy measurements. MgO layers are characterized by sharp interface with the substrate and limited surface roughness, besides good chemical uniformity and polycrystalline structure for thickness above 7 nm. C–V measurements performed on Al/MgO/Si MOS capacitors, with MgO in the 4.6–11 nm thickness range, allow determining a dielectric constant (κ) ∼ 11. Co layers are grown by chemical vapour deposition in direct contact with MgO without vacuum-break (base pressure 10−5–10−6 Pa). The as-grown Co/MgO stacks show sharp interfaces and no elements interdiffusion among layers. C–V and I–V measurements have been conducted on Co/MgO/Si MOS capacitors. The dielectric properties of MgO are not influenced by the further process of Co deposition. [ABSTRACT FROM AUTHOR]

The article explores the benefits presented by imaging technologies in endometriosis management. Since endometriosis appear in three different forms, different imaging diagnostic processes can be used to better study and define the complex syndrome. Endometriomas, deep implants and adhesions are the common sonographic findings, with endometriomas presenting a variety of sonographic appearance including diffuse low-level internal echoes. In 2011, Hudelist and his colleagues were able to prove the accuracy of using sonography for non-invasive detection of deep endometriosis and pre-surgical assessment. As evaluation of bladded and ureters is important in the staging of endometriosis, magnetic resonance imaging has been proven to be suboptimal in detecting endometriosis.

High dielectric constant (high-κ) oxides are foreseen replacement materials in innovative metal-oxide-semiconductor devices and memory capacitors. In particular, when considering nonvolatile memories, the charge-trapping concept appears to be a promising solution for flash-type floating gate replacement. Among the high-κ oxide properties to be considered, it is essential to study the compatibility towards the integration of these materials in a complementary metal-oxide-semiconductor process, in particular to control the stack integrity and any onset of diffusion phenomena upon thermal treatments at temperatures higher than 1000 °C. Here, we report on the results obtained from time-of-flight secondary ion mass spectrometry depth profiling of stacks on the basis of high-κ/SiO2/Si, integrating HfO2, ZrO2, or DyScOx as charge-trapping layer or high-κ/SixNy/SiO2/Si integrating DyScOx as control (blocking) oxide. The high-κ oxides are all grown by atomic layer deposition. We will discuss the role of the different substrate/oxide coupling in preserving the stack and propose the better combinations in terms of thermal stability. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Arrays of vertical nanowires structured in Au/NiO/Au segments with 50 nm diameter are characterized by conductive atomic force microscopy to investigate unipolar resistive switching in NiO at the nanoscale. The switching cycles are characterized by extremely low power consumption down to 1.3 nW, which constitutes a significant improvement in nanowire-based resistive switching memory devices. The trend of the reset current as a function of the set resistance, typical of unipolar memories, is extended to a much wider current range than what is reported in literature, confirming the role of Joule heating in the reset process for very low reset currents. [ABSTRACT FROM AUTHOR]

We have investigated the atomic layer deposition (ALD) on SiO2 and III-V (i.e., In0.53Ga0.47As) substrates of Al-doped ZrO2 (Al-ZrO2) films. The aim is to benefit from trimethylaluminum-based chemistry as adopted in the ALD of Al2O3 while concomitantly obtaining an improvement in the value of the dielectric constant of the gate stack. An in situ monitoring of the process with spectroscopic ellipsometry was carried out in order to address the formation of the first few monolayers of the films. The correlation with the structural and chemical characterization provides insights about the interface composition upon ALD. A k value of 19 ± 2 is demonstrated for Al-ZrO2 films deposited on SiO2. The electrical performances of capacitors fabricated on In0.53Ga0.47As including Al-ZrO2 as gate dielectric exhibit encouraging properties compared to those acquired for Al2O3. However, a further optimization of the interface reactivity in order to prevent the formation of undesired In, Ga and As oxidized species appears still needed for the combination of the Al2O3 and ZrO2 ALD processes. [ABSTRACT FROM AUTHOR]

Among the widespread range of applications in which ZrO2 thin films are of interest, they are receiving a peculiar consideration as candidate replacement material in innovative microelectronic devices, such as non volatile memories. In this work, we deposited ZrO2 films on Si (100) substrates by atomic layer deposition at 300°C from (MeCp)2ZrMe(OMe) as Zr precursor and using, H2O or O3 as oxygen source. After deposition films were subjected to rapid thermal annealing at 800°C for 60 s in N2. Film thickness is calculated from X-ray reflectivity to be in the 5-60 nm range. Grazing incidence X-ray diffraction reveals that the film crystallographic phase is highly influenced by the oxidizing agent used during the deposition process. While the use of H2O gives films consisting of mixed phases, the monoclinic phase is almost absent in films deposited employing O3, which stabilize in the ZrO2 cubic/tetragonal phases. Upon annealing, the films retain their crystallographic structure, despite a marginal increment of the monoclinic phase. Time of flight secondary ion mass spectrometry depth profiles evidence film uniformity and thermal stability. The evolution of electrical properties of ZrO2 films is discussed as a function of oxygen precursor and thermal treatment. The measured dielectric constant values after 800°C annealing are κ∼24 and κ∼30 in the films deposited using H2O or O3 respectively, in agreement with the different crystallographic phases in the ZrO2 films. [ABSTRACT FROM AUTHOR]

In the view of improving standard TANOS stacks, a possible route is the replacement of Al2O3 blocking oxide with materials with higher dielectric constant κ, as this would increase the electric field across the tunnel oxide. A possible solution is to integrate rare earth scandates. Among the scandates, DyScO3 appears as an attractive material due to the reported high-κ value. Films with 10-30 nm nominal thickness were grown by atomic layer deposition (ALD) on Si substrates for process optimization and structural characterization. Sc(thd)3 and Dy(thd)3 were used as Sc and Dy precursors and O3 as oxidizing agent. First, Sc2O3 and Dy2O3 growth process was optimized by changing growth temperature (Tg) and ALD cycle. The best conditions for the deposition of the ternary DyScO films were found to be Tg=350 °C and Dy:Sc=1:1 pulsing ratio. Optimized films were also grown on Si-rich SiN for integration as blocking oxide. After deposition, films were subjected to rapid thermal annealing up to 1030 °C to check their thermal stability. Film thickness was checked by x-ray reflectivity, together with roughness and electron density. Film crystallinity was investigated by grazing incidence x-ray diffraction. Film uniformity and thermal stability were explored by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiles. Dielectric constant κ was extracted from capacitance-voltage (C-V) electrical measurements. As deposited amorphous DyScO films on silicon remain amorphous after annealing up to 900 °C. Film electron density reduces while thickness increases with annealing, surface roughness remaining at ∼1.5 nm. The measured Sc:Dy atomic ratio by total x-ray fluorescence analyses is 1.33 in the as deposited film. ToF-SIMS depth profiles showed that film uniformity and composition is not preserved at 900 °C, in films deposited on Si, as major Si diffusion affects the ternary oxide. Only at 600 °C the diffusion phenomena and film composition are preserved. The extracted DyScO dielectric constant is κ∼20 in films annealed at 600 °C on Si. When deposited on Si-rich SiN, DyScO uniformity remains well preserved up to 900 °C, with an improvement of the thermal stability with respect to deposition on Si. Si diffusion is evident at 1030 °C only. The κ-value extracted from C-V resulted to be κ∼20. [ABSTRACT FROM AUTHOR]