Wolfgang Wondrak
Daimler AG
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Featured researches published by Wolfgang Wondrak.
IEEE Transactions on Industrial Electronics | 2001
Wolfgang Wondrak; Raban Held; Ekkehard Niemann; Ulrich Schmid
Silicon carbide (SiC) process technology has made rapid progress, resulting in the realization of very promising electronic devices and sensors, enabling advanced solutions in power industry and mobile systems. In particular, for electronics working under harsh environmental conditions, SiC devices reach unprecedented performance. Transfer to production has already started for some applications.
Microelectronics Reliability | 1999
Wolfgang Wondrak
Abstract In many applications of electronics, a growing demand for devices being capable of operating at increased temperatures is developing. In automotive and aerospace industry, the replacement of mechanical or hydraulic systems by electronics requires harsh environmental conditions. Furthermore, the oil-well business, military, industrial, chemical, and consumer electronics show increasing interest in higher operating temperatures. In this paper, the influence of temperature on semiconductor device characteristics is discussed with regard to physical limits for device operation. Different semiconductor materials are compared with respect to high temperature electronics, and an overview of the state-of-the-art of high-temperature devices is given. With standard silicon technology, high operation temperatures (200°C) can be reached with reduced performance, the use of SiC enables electronic devices for much higher temperatures (600°C). For practical use, device lifetime becomes the limiting factor at increased temperatures, especially chip metallisation systems and packaging technologies are critical factors for device lifetime in most cases.
Microelectronics Reliability | 2002
A. Dehbi; Wolfgang Wondrak; Yves Ousten; Yves Danto
Abstract Nowadays, many innovations in the automobile are enabled by electronics. Ambient requirements can be very stringent especially when the temperature reaches 150 °C or even more. Especially electrolytic capacitors are known to be critical devices at high temperatures. Therefore, it is necessary to validate the performance of such components and check their reliability during high temperature operation. In this paper we discuss how to predict the lifetime of both aluminum and tantalum electrolytic capacitors. In that aim we first review state of the art qualification tests that allow a life prediction. We describe a test setup that we have built in order to investigate electrolytic capacitors by LCR and leakage current measurements at temperatures above current manufacturers specifications. Results for different capacitors after variation of tests conditions will be presented.
international symposium on power semiconductor devices and ic's | 1992
Wolfgang Wondrak; R. Held; E. Stein; Jacek Korec
The concept for a design of high-voltage SOI-devices presented in this paper can be easily incorporated in standard silicon direct bonding (SDB) technology and enables a fabrication of lateral devices with breakdown voltages of more than 6OOV in 2-10pm thick SO1 layers. For such devices, the dependences of the breakdown voltage on the silicon layer thickness, on the doping concentration, and on the buried oxide thickness are discussed.
IEEE Transactions on Electron Devices | 2000
Ulrich Schmid; Scott T. Sheppard; Wolfgang Wondrak
Electrical characterization up to 573 K is performed on integrated inverters with different beta ratios and 17-stage ring oscillators based on SiC NMOS technology. These devices are fabricated on a p-type 6H-SiC epitaxial layer with a doping concentration of N/sub A/=1/spl middot/10/sup 16/ cm/sup -3/. The n/sup +/ source/drain regions and buried channels for depletion-mode load transistors are achieved by ion implantation of nitrogen. Direct current measurements of the inverters with a 5 V power supply yield proper output levels and acceptable noise margins both at 303 and 573 K. Dynamic measurements with square waves show the full voltage swing up to 5 kHz in this temperature range. The 17-stage ring oscillators, driven by a 5.5 V power supply, show an oscillator frequency of 625 kHz at 303 K, which corresponds to a 47 ns delay per inverter stage. This time constant increases only to 59 ns at 573 K. The temperature drift of the measured output signal is well below 30% up to this elevated temperatures. During 20 heat cycles up to 573 K in air, no measurable drift in circuit parameters occurred. In addition, only a slight dependence of the oscillator frequency on supply voltage is observed.
Materials Science and Engineering B-advanced Functional Solid-state Materials | 1999
F. Wischmeyer; Wolfgang Wondrak; D. Leidich; Ekkehard Niemann
Abstract In this paper we have investigated the CVD growth of 3C-SiC on SOI (100) substrates at reduced temperatures employing a carbonization step with a slow temperature heating-ramp. The carbonization leads to a rapid sealing of the Si-top layer of the SOI substrate due to a high SiC nucleation density totally avoiding the commonly reported formation of cavities at the 3C-SiC/Si interface. From TEM investigations it can be shown that the crystallinity of the 3C-SiC is comparable to state-of-the-art SiC thin films on Si. Exploiting this growth process 5 μm thick 3C-SiC layers on Si (100) show excellent crystal quality with a FWHM=0.18° derived from X-ray ω -rocking curves. This is confirmed by electrical characterization using Hall measurements.
Journal of Applied Physics | 1999
Ulrich Schmid; R. Getto; S. T. Sheppard; Wolfgang Wondrak
The electrical characteristics of TiSix contacts to nitrogen implanted 6H-SiC are investigated using linear transmission line method structures at temperatures up to 673 K. Nitrogen is implanted into a p-type (NA≈1×1016 cm−3) 6H-SiC epilayer at 500 °C and activated at 1700 °C, resulting in an activated donor concentration of ND=5×1019 cm−3 to a depth of 300 nm with a reduced electrically active surface concentration of about ND≈5×1018 cm−3. Sputtered titanium silicide is used as contact metallization. Five different contact formation temperatures TA ranging from 900 to 1150 °C are applied to the samples in order to investigate the specific contact resistance ρc. Whereas an anneal of at least 950 °C is necessary to achieve an ohmic contact behavior, samples annealed at 1150 °C show specific contact resistance of 7×10−6 Ω cm2 at room temperature, which decreases monotonically to 4×10−6 Ω cm2 at 673 K. The sheet resistance Rs (resistivity ρs) of the n+-implanted layer is 521 Ω/□ (15.6×10−3 Ω cm) at 303 K. Up...
Microelectronics Reliability | 2005
A. Dehbi; Yves Ousten; Yves Danto; Wolfgang Wondrak
Abstract Automotive requirements are nowadays not only limited to high temperatures but more and more demands are driven towards vibration and higher acceleration values due to the direct mounting of the Electronic Control Units on the Engine. Temperature cycle testing and combined testing methods have been under study for a long time but literature concerning Vibration Modelling is very poor in comparison with thermal models like Arrhenius or thermo-mechanical based models like Coffin-Manson. In this article, a revisit of the Steinberg Model is presented with a direct application on tantalum capacitors populated boards. Experimental results with various sinusoidal excitation g-level are presented; whereas on the other side FEM simulations are performed and results are implemented in the Steinberg Model, in order to identify model parameters.
Microelectronics Reliability | 2005
Ha Post; P. Letullier; T. Briolat; R. Humke; R. Schuhmann; K. Saarinen; W. Werner; Yves Ousten; G. Lekens; A. Dehbi; Wolfgang Wondrak
Abstract New electronic architectures and mechatronic integration in automotive and oil-field applications lead to increasing requirements concerning operating temperatures and vibration levels. At the same time, reliability and lifetime have to fulfil strong demands. In the European funded project PROCURE (Program for the development of passive devices used in rough environments) a generic spectrum of passive components needed for electronic control units has been developed. The failure mechanisms, the technological challenges, and the test requirements are highlighted below.
Microelectronics Reliability | 2000
Jean Manca; Wolfgang Wondrak; W. Schaper; K. Croes; J. D’Haen; W. De Ceuninck; B. Dieval; Hans L. Hartnagel; Marc D'olieslaeger; L. De Schepper
Abstract Gate oxide reliability and thermal shock resistance of power MOSFETs for high temperature applications, have been investigated by accelerated tests and several analytical and electrical techniques. Thermal shock tests have been performed between -40°C and 200°C with subsequent electrical tests and failure analysis. Time Dependent Dielectric Breakdown (TDDB) of the gate oxide has been studied in detail by means of in-situ leakage current measurements at various voltages and temperatures.A statistical analysis of the results yields information on the underlying failure time distribution, failure mechanisms and lifetime.