Very thin carbon films were deposited by electron beam-plasma vacuum deposition technique on quartz and sapphire substrates. The concentration of elements was determined by RBS and ERD analytical method simultaneously. Concentrations of elements were practically the same for all samples. Raman spectroscopy and deconvolution of Raman spectra was used for chemical structural features determination of carbon films. Raman spectroscopy results showed that films contained several carbon phases. The photo-induced electron emission characteristics of very thin carbon films on quartz and sapphire substrates as back-side illuminated transmission photocathode are discussed. Best electron emission properties exhibit transmission photocathode with very thin carbon film prepared on sapphire substrate at lower substrate temperature.
An optimization of electrical, thermal, and mechanical properties of SiC MOSFET transistors supported by advanced effective 3-D electro-thermal device simulation is presented. The developed simulation method is capable of a full analysis of complex structures with a high speed of simulation and simple implementation. The simulation method is utilized for electrical and thermal analysis of power SiC MOSFET. Two bonding methods of SiC MOSFET transistor are analyzed and compared. Simulation results demonstrated that the optimized clip-bond concept has better electrical and thermal performance than the wire-bond.
This paper investigates the robustness and reliability issues of commercial 1.2-kV 4H-SiC MOSFETs under repetitive unclamped inductive switching (UIS). The degradation of device characteristics, including the transfer characteristics, drain leakage current $I_{dss}$ , and output characteristics, is observed. A significant increase in leakage current was observed after relatively short avalanche stress (UIS stress), and device destruction occurred after 30 million of cycles. Besides the shift of static electrical characteristics, also a change in switching times was observed. The hot carriers injection and trapping into the gate oxide and its interfaces is believed to be responsible for the variation of electrical parameters.
Incremental capacity analysis (ICA) and Galvanostatic Intermittent Titration Technique (GITT) are commonly used tools of electrical characterisation of degradation of Li-ion batteries. Disadvantage of these methods is their significant time consumption since both of these methods are based on charging/discharging by very low currents (e.g. C/20). In this contribution we propose a novel approach of performing ICA analysis via utilisation of GITT data in order to significantly decrease time of the measurements and/or include ICA analysis into GITT measurements, which would not be otherwise performed.
This paper presents the practical solutions for measuring small currents at the characterization of organic field-controlled transistors. It presents the design, PCB layout, and methodology of various small current measurement principles. The design mainly focuses on a trans-impedance amplifier that transforms current into voltage. In this paper, we can also determine the critical parameters for selecting the main components in the measuring part. Also, simulations and measurement of real measured parameters with an evaluation of all critical quantities, such as accuracy, precision, linearity, offset, noise, and response speed.
Within this paper a test system is introduced which is able to cycle multiple discrete power semiconductors in a hybrid manner within a wide temperature range, based on arbitrary programmable temperature mission profiles. Based on these profiles active power cycling is performed in combination with different static climatic conditions. The aim of this kind of test is to emulate the real thermal stress the device would undergo in harsh environments, where strong temperature changes could lead to a faster degradation of the device. With this approach the reliability of the device can be evaluated without the need for a lifetime model, as it is based on standard temperature cycling methods.
In this work, we have carried out a detailed transmission electron microscopy investigation on ohmic contacts in InAl GaN/GaN high electron mobility transistors consisting of Ti/Al/Ni/Au deposited by evaporation electron beam followed by a rapid thermal annealing at 875°C for 30s under N2 atmosphere. Subsequent to an optimized surface preparation, prior to the metal deposition, it has been possible to systematically obtain a contact resistance of 0.15-0.16 Ω.mm instead of the usual 0.5-0.6 Ω.mm. This is comparable to the state of the art results which have been published subsequent to more complex processes including molecular beam regrowth.
Based on the finite element (FE) simulations done in this work, lowering the bonding temperature significantly decreases the bonding induced residual stresses. Therefore, low temperature Cu-Sn-In SLID process was utilized to bond Si to Si and Si to sapphire under various bonding conditions. The microstructural evolution and the (thermo-) mechanical properties of the joints were studied. The results showed that the Cu-Sn-In SLID bonds composed of a single Cu 6 (Sn, In) 5 IMC phase with high joint strength. Furthermore, the hardness and Young's modulus of Cu 6 (Sn, In) 5 formed in the SLID bonding were measured to be slightly higher than that of binary Cu6Sn 5 .
This paper deals with an overview of mechanical-electrical systems used in generating electrical energy for the purpose of powering secondary systems controlling access control systems. In practice, we can meet them, for example, in administrative buildings, where they serve as sources of electricity for autonomous systems for the authorization of workers in the house. GaN transistors are also beginning to be used in this area and their use leads to higher energy gains.
In this work, we present a pressure sensor based on piezoelectric response of a thin 100 nm ZnO 002-oriented film grown using atomic layer deposition (ALD) technique on a commercial Si 3 N 4 membrane. In contacts on top of the ZnO film allowed measuring the piezoelectric response laterally along the ZnO film induced by the pressure difference causing mechanical deflection of the membrane. The ALD of ZnO is the key process here, where the growth characteristics were investigated in order to obtain 002-oriented piezoelectric ZnO films. A linear response of this sensor in the 0.2-1.0 kPa range was recorded.
Silicon carbide (SiC)- based power modules in automotive applications are becoming more and more important in the framework of battery and hybrid vehicles. Consequently, the reliability concerns related to these products must be carefully assessed, considering the harsh environment of automotive applications. The aim of this work is to give some insights into the reliability assessments during the design stage of SiC modules devoted to traction applications, considering different aspects such as power cycle, thermal characterization, and solder joint reliability.
In this paper, the results of Thermally Stimulated Depolarization Currents (TSDC)-measurements of a complex system of stacked dielectric layers, like typically appearing in semiconductor packages, is presented. Characteristics of the individual isolation layers are presented solely and the results are compared to the stack. The investigated layers are comprising polyimide film, alkali-free glass, polyolefin film and epoxy based mold compound. Measurements have been carried out in the temperature range from 19 - 195°C at varying polarization fields for every material. Various relaxation peaks, originated by different polarization mechanisms within the materials could be observed. A comparison between the TSDC-peaks of the layer stack and the individual materials is shown. Our results demonstrate, that the super positioned spectrum is getting dominated by a single portion, the mold compound.
Major trend in Microelectronics is the move towards higher system integration driving increasing compactness and complexity and all at acceptable cost. This paper presents an overview on selected results from the ECSEL JU project iRel40 which has the ultimate goal of improving reliability of electronic components and systems by reducing failure rates along the entire value chain. We first present an aspect for development, where digital twins are applied to develop and design an optimum assembly and packaging. Then we highlight that preassembly, intelligent data handling applied in production, and the importance of material and testing knowhow have impact to improve reliability.
Todays state of the art of predictive high-fidelity computer simulation of “failure and virtual destruction” is illustrated with reference to selected real-life examples as encountered in electrical energy technology. It aims in particular at high-power devices employed in the generation and recovery, the transmission and distribution, and the consumption of electrical power in our modern high-tech societies, which in future have to rely on regenerative energy sources like wind farms and photovoltaics, highly efficient power grids, and environment-friendly trans-portation like electromobility. All this is today supported by realistic computer simulations on the basis of well-calibrated physical device models. The challenge is to make virtual experiments and tests on the computer, which are qualitatively reliable and quantitatively accurate even for device structures that have never been built before, and under operational conditions that very rarely occur as long as the device is kept within the “safe operating area (SOA)”. What we are interested in is to explore the rim of the SOA and even to go beyond it in order to study failure and, eventually, destruction mechanisms with a view to improving robustness and reliability of the devices.
In this contribution, we deal with PEDOT: PSS organic electrochemical transistors (OECTs), which pose a perspective device for biosensing applications. We manufactured two transistors with electrolysis prepared Ag/AgCl electrode, and commercial one. Commercial one, reached better current stability, therefore we propose PEDOT: PSS (GOPS) benchmarking according to it. PEDOT: PSS films were prepared by perspective inkjet printing and crosslinked by GOPS. There is still a space for optimization to reach biosensing ready device.
In this paper we investigate different polymer coatings to improve robustness in Systems in Packages (SiP) devices for high performance and energy efficient RF-and mm-wave power amplifiers. Cheaper and denser integration of GaN and Si technologies is required. We studied final polymer protection coatings on the semiconductor chip that delay the corrosion phenomenon. Our first results show that BCB seems to be the most efficient protective solution, but there are other materials that could be considered, either for lower dielectric constant or for outstanding electric field handling capability.
In this paper we have aimed at the detectors based on the high-quality 4H-SiC epitaxial layer operated at increased temperature. The 4H-SiC is a wide-band-gap semiconductor material with favourable properties for radiation detectors like radiation tolerance and chemical stability. The prepared detectors had an active thickness of 50 µm. The active area was defined by the prepared Ni/Au Schottky contact with a circular shape and a 3.0 mm diameter. The current-voltage characteristics of prepared detectors were measured up to 300 V at different temperatures to determine the operating voltage region. The precise temperature stabilization system was developed to realize detector measurements at different temperatures. Prepared detector structures were tested with a-particles generated by a 238 Pu 239 Pu 2448 Cm radioisotopes. The 4H-SiC detector shows high-energy resolution at room and even elevated temperatures and is able to resolve two close energies generated by an alpha particle radiation source.
This paper deals with identifying electrically active defects and determining their fundamental parameters in InAlGaN/GaN HEMT structures by Deep Level Transient Fourier Spectroscopy (DLTFS) with optical excitation. Parameters of 5 electron-like defects and three hole-like defects were confirmed by DLTFS method. Parameters of 9 hole-like defects common to both structures were identified by DLTFS-O. Two hole-like defects were confirmed by both methods: DLTFS and DLTFS-O methods. The probable origin of electron-like defects could be nitrogen vacancies, defect clusters along screw- and mixed-type dislocations, the presence of surface states or emissions from the interface. The probable origin of hole-like defects could be the presence of surface states or defects in barriers. The benefits of different method utilization were confirmed by experimental results.
The paper presents part of results of double-pulse switching tests and extraction of dynamic on-resistance of packaged normally-off GaN HEMTs. Devices were tested under various switching conditions. Effects of the switching parameters on dynamic on-resistance were analysed and compared. Samples were exposed to repetitive SC stress for several thousand repetitions of switching. Shift of on-resistance due to short-circuit stress was observed, but not of significant magnitude.
Advanced Process Control (APC) systems monitor semiconductor manufacturing processes continuously via equipment internal sensors. The logged data enables data-driven predictive maintenance approaches. Integration of APC-derived constraints into scheduling has the potential to improve the overall equipment effectiveness (OEE). Therefore, we introduce a real-world semiconductor manufacturing case study: Ion Implantation equipment accelerates dopants in an electric field onto wafers, to change electrical properties of defined layers. Every recipe change necessitates ion beam tuning, to meet specifications under varying equipment conditions. In order to avoid expensive timeouts of unsuccessful tuning, a prediction model estimates the tuning success and scheduling is (to be) optimized accordingly. Our preliminary results show that more than half of unsuccessful ion beam tuning can be correctly predicted and thus avoided.
