Electron Beam Induced Damage on Passivated Metal Oxide Semiconductor Devices

Electron beam testing of integrated circuits (IC) is currently based on the electron beam induced conductivity in insulators to short the passivation layer and to enable a voltage measurement at covered conductor tracks. However, applying this technique to passivated MOS devices causes severe radiation damage, which was at first explained by primary electrons penetrating into the deep-lying gate oxide. Nondestructive electron beam testing was expected by using low electron energies that do not allow the primary electrons to reach into the gate oxide. Therefore here the influence of nonpenetrating electron irradiation on the characteristics of passivated NMOS transistors has been studied. The experiments demonstrate that significant damage is caused even when primary electrons do not reach into the gate oxide. This can be explained by secondary X-rays, generated by the primary electrons in the upper layers, that then penetrate into the gate oxide. Radiation damage increases with irradiation dose, primary energy and with decreasing gate size. Though using the lowest primary electron energy possible to build up the necessary conductive channel, even low irradiation doses alter the devices drastically. Only by blanking off the high energy electron beam at gate oxide areas during the scan, i.e. by application of the window scan mode, is a nearly nondestructive testing of passivated MOS devices via the electron beam induced conductivity made possible. Another possibility to decrease radiation damage is the reduction of primary electron energy to about 1 keV. Then electron beam testing is no longer based on the physics of electron beam induced conductivity, but on the capacitive coupling voltage contrast

Scanning Probe Microscope Gigahertz Measurements on 200 Nanometer Wave Guides

Scanning probe microscopy is opening new applications in microelectronic engineering due to easy and reliable instrumentation in combination with superior resolution limits without any sample preparation under ambient conditions. Beside the standard topography imaging possible application are static and dynamic surface potential measurements, doping profiling, and scanning thermal applications. In this paper, we report dynamic voltage contrast measurements of analog and digital gigahertz signals on 200 nm wave guides within integrated microelectronic devices and components. The results are obtained by using a time resolved device internal test technique based on a scanning force microscope using the electrostatic force interaction. This technique enables voltage contrast even within passivated integrated circuits with nanometer spatial resolution and gigahertz measurement bandwidth and additionally millivolt sensitivity

Computer Simulation and Experimental Performance Data for an Electron Spectrometer for Electron Beam Testing of Integrated Circuits

Electron beam testing using voltage contrast in the scanning electron microscope has been established as a useful tool for nondestructive and nonloading functional testing and failure analysis of integrated circuits (IC). The accuracy of quantitative voltage measurements within the IC with the electron beam probe is determined by the performance of the secondary electron (SE) spectrometer used. For simulating the performance of SE-spectrometers a program-package has been developed by aid of which the voltage-and field-distributions within the spectrometers can be evaluated using a finite element method. Thus it is possible to trace electron trajectories throughout the spectrometer. By considering a great number of SE-trajectories, the detected integral SE-signal for different voltages at the IC can be determined as a function of the retarding field voltage within the spectrometer. In this way the performance of an existing spectrometer is simulated. The experimentally measured SE-signals are compared with the simulation data. This comparison showed that the program-package realistically simulates the spectrometer properties. Therefore this program-package enables an improvement of existing SE-spectrometers and in principle also the development of new spectrometer-assemblies. Here the suitability for optimizing a SE-spectrometer is shown

A Contribution to the Scanning Electron Microscope Based Microcharacterization of Semi-Insulating Gallium Arsenide Substrates

The macroscopic behaviour of semiconducting materials is determined by the distribution of microscopic defects like dislocations, impurities and intrinsic defects. Therefore, microanalytical methods are necessary to control the influence of technological process parameters on the materials properties. In the case of GaAs substrates, measurements of the cathodoluminescence (CL) and the electron beam induced voltage (EBIV) as well as the new charging technique seem to be promising methods to perform this task. CL-micrographs of as-grown GaAs substrates show bright cellular structures, which correspond to dislocation networks. Comparative investigations by use of the new charging contrast technique indicate an increased conductivity in the bright areas. CL-measurements of annealed substrates reveal additional characteristic island-like structures in the cell interior. Both, cellular and island-like structures can also be visualized by the EBIV technique. These results can be explained by a homogeneous conductivity and an inhomogeneous distribution of the excess carrier lifetime

Impacts of Multiscale Predictors on Random Forest Based Probabilistic Forecasts of Severe Weather Hazards

Machine learning (ML) algorithms utilized for post-processing of convection-allowing model/ensemble (CAM/CAE) output has been a major area of research to handle limitations with CAM/CAE forecasts. ML has been used to correct systematic biases, relate observed variables to numerical output, and synthesize extremely large data into probabilistic forecasts. In particular, numerous studies have shown random forests (RFs) to be successful in severe weather forecasting applications utilizing predictors from global scale and/or CAE output. However, predictors used in the RF models are typically fixed and treated independently when training the RF models. This can consequently leave out important information about the large-scale flow pattern that is necessary for assessing severe weather risk. This thesis develops a method for manifesting multiscale flow-dependence into RF models through direct incorporation of CAE-based predictors that are pre-processed at increasing spatial length scales. The different length scales account for different scales of motion with the goal to improve probabilistic forecast skill for a variety of severe weather hazards for next-day (12-12 UTC) - or 24hr and 4hr (20-00 UTC) forecasts. In order to verify the impacts of the multiscale predictors on the skill of the RF models, a control (CTLRF) and experimental (EXPRF) set of RF models were created. The CTLRF models were trained with only predictors pre-processed to 80 kilometers (km) and the EXPRF models were trained with predictors pre-processed to 80 km in addition to larger, spatially smoothed 80 km predictors. Both models were verified against the storm prediction center (SPC) reports quantitatively and qualitatively. Results show that the EXPRF models had higher brier skill score’s (BSS) than the CTLRF models for all sub-significant severe weather hazards for both forecast periods, but significantly higher BSS’s when forecasting any severe weather hazard (24hr and 4hr), wind (24hr), hail (24hr and 4hr), and significant winds (24hr). The EXPRF forecasts generally had the best resolution component of the brier score (BS), of which some severe weather hazards were significantly higher than CTLRF forecasts. Furthermore, both models generally had small calibration error. However, the CTLRF 24hr and 4hr wind forecasts had significantly lower calibration error compared to EXPRF. In general, neither model’s probabilistic forecasts were consistently more reliable than the other. Predictor contributions determined via tree interpreter (TI) showed when severe weather did not occur, on average, the meso-γ scale storm-attribute predictors contributed more to forecast skill than the meso-β scale storm-attribute predictors for 24hr forecasts. Whereas the opposite was true for the 4hr forecasts. When severe weather did occur, on average, the meso-β scale storm-attribute predictors contributed the most to skill in general. Meanwhile, the meso-γ scale environmental predictors dominated environment-related contributions to forecast skill, but in general, most multiscale predictors still contributed to skill. Through case-studies, it was found that the meso-β and meso-α scale storm-attribute predictors accounts for spatial uncertainty of simulated storms similar to neighborhood-based CAM forecasts. Meanwhile the environment predictors, in particular the convective environment predictors, had greater sensitivity to smoothing and sometimes did not benefit from losing sharp gradients and local extremes that can be associated with synoptically predictable features

Electron Beam Testing of Passivated Devices via Capacitive Coupling Voltage Contrast

By fundamental experiments and theoretical treatments a detailed understanding of the capacitive coupling voltage contrast {CCVC) has been gained, demonstrating that this technique is, in principle, applicable to a non-destructive testing of passivated integrated circuits (IC) by means of electron beams. In fact, however, several problems have to be eliminated in order to introduce this testing technique into a production line procedure. In a first step, preconditions have to be met. These are a primary electron (PE) energy where the electron yield is greater than one and a sufficiently low extraction field above the IC. Secondly, as CCVC vanishes within a certain time span caused by charge compensation during electron irradiation, several precautions have to be undertaken. To obtain unfalsified CCVC-micrographs a fast image recording and processing system has to be realized; for IC-internal waveform measurements suitable sampling electronics have to be developed. Besides this, the resulting measurement errors are classified and determined. These are the error due to charge compensation on the passivation layer during electron irradiation, the error due to an incomplete coupling of the line potential to the passivation surface and the error due to capacitive coupling cross talk from neighboring lines

Posrtaji reforme strukovne Povijesti

Osvrt na događanja u prvoj polovici 2023. godine vezano u najavu reforme kurikluma srednjih strukovnih škola u Hrvatskoj. Autorica izvještava o skupu strukovnih škola u organizaciji Agencije za strukovno obrazovanje i osposobljavanje odraslih. Kronološki prati akcije nastavnika povijesti kojima nastoje sačuvati satnicu predmeta Povijest u strukovnim školama. U prilozima su: pismo nastavnika Ministarstvu, obavijest profesorima, pismo saborskim zastupnicima, pismo Društva za hrvatsku povjesnicu i pismo Hrvatske udruge nastavnika povijesti

Capacitive Coupling Voltage Contrast

Capacitive coupling voltage contrast (CCVC) allows electron-beam testing of passivated integrated circuits (IC) without radiation damage or prior, time-consuming specimen preparation. This effect occurs when low primary electron energies are used and the electron yield of the passivation layer is greater than 1. Signal changes in the relevant interconnections are transferred to the passivation surface via capacitive coupling, but they vanish there within the storage time due to electron irradiation. A physical model explains the dependence of CCVC on three parameters: electron irradiation, the passivation material and the signals within the IC. Computer simulations based on this model describe the experimentally-obtained dependencies of the storage time with precision and al low predictions to be made for using CCVC in electron beam testing. The requisite modifications to the electron beam testing system are described and the possible uses of CCVC for testing passivated devices within IC are demonstrated on the basis of examples

Orientation and structure of the Ndc80 complex on the microtubule lattice

The four-subunit Ndc80 complex, comprised of Ndc80/Nuf2 and Spc24/Spc25 dimers, directly connects kinetochores to spindle microtubules. The complex is anchored to the kinetochore at the Spc24/25 end, and the Ndc80/Nuf2 dimer projects outward to bind to microtubules. Here, we use cryoelectron microscopy and helical image analysis to visualize the interaction of the Ndc80/Nuf2 dimer with microtubules. Our results, when combined with crystallography data, suggest that the globular domain of the Ndc80 subunit binds strongly at the interface between tubulin dimers and weakly at the adjacent intradimer interface along the protofilament axis. Such a binding mode, in which the Ndc80 complex interacts with sequential α/β-tubulin heterodimers, may be important for stabilizing kinetochore-bound microtubules. Additionally, we define the binding of the Ndc80 complex relative to microtubule polarity, which reveals that the microtubule interaction surface is at a considerable distance from the opposite kinetochore-anchored end; this binding geometry may facilitate polymerization and depolymerization at kinetochore-attached microtubule ends