Ralf Siemieniec

Determination of parameters of radiation induced traps in silicon

Abstract Irradiation techniques are nowadays widely used for carrier lifetime adjustment in silicon power devices because of their very good reproducibility. But still there are missing or incomplete recombination center data for use in device simulation. Based on DLTS and lifetime measurements, the center properties of the most important traps after electron irradiation and annealing with a temperature above 330 °C are determined in this work within a wide temperature range. These parameters have been used for device simulation of irradiated power diodes and correctly explain the temperature dependencies of forward voltage as well as of switching characteristics.

Possibilities and limits of axial lifetime control by radiation induced centers in fast recovery diodes

Device simulation, based on an extended recombination model, is used as a design tool for lifetime-controlled power diodes with different lifetime profiles. Homogenous and local recombination center profiles are considered. The sensitivity of important device properties, such as the trade-off between stationary and dynamical characteristics, to the recombination center peak position is investigated. The occurrence of dynamic impatt oscillations is analyzed.

Application of carrier lifetime control by irradiation to 1.2kV NPT IGBTs

Device simulation, based on an extended recombination model and previously determined recombination center parameters, serves as design tool for carrier-lifetime controlled, state-of-the-art 1.2kV NPT IGBTs. Homogenous and local recombination center profiles are considered. The sensitivity of important device characteristics to the type of the recombination center profile is investigated in simulation and experiment. A possible application, the improvement of reverse leakage properties of reverse blocking capable NPT IGBTs, is discussed.

The plasma extraction transit-time oscillation in bipolar power Devices-Mechanism,EMC effects, and prevention

Under certain conditions, radio frequency (RF) oscillations may occur during the turn off of bipolar power devices. These oscillations are related to the plasma extraction transit time (PETT) effect. The mechanism of the oscillation and the complex dependencies for the occurrence of the effect are discussed in this paper. Three-dimensional electromagnetic compatibility (EMC) simulation is used to investigate modifications of the power module layout that shift its resonance point and therefore, effectively suppress the unwanted RF oscillations. EMC measurements and examples of failures of power electronic equipment related to the occurrence of PETT oscillations demonstrate the necessity for suppressing this effect.

Analysis of dynamic impatt oscillations caused by radiation induced deep centers

The occurrence of high-frequency impatt oscillations is related to the presence of charged deep donor-states as generated by irradiation processes for carrier-lifetime control. This effect is well-known in electron-radiated devices. Device simulation predicts a similar effect in locally lifetime-controlled helium-radiated devices. The experiment gives an approval of the simulation results but shows some unexpected effects too.

Applying device simulation for lifetime-controlled devices

Irradiation techniques are widely used for carrier lifetime control in power devices. Improvements of irradiated devices were usually realized by a number of experiments. The use of an extended recombination model allows improved device simulations which explain the temperature dependencies of stationary and dynamical characteristics. Due to that progress device simulation is able to support development and optimization of irradiated devices.

Multi-cell effects during unclamped inductive switching of Power MOSFETs

In this paper, we describe the crucial dependence of avalanche behavior on epitaxial layer thickness and gate resistance during undamped inductive switching (TJIS) especially for high currents for power MOSFET devices employing field-plate compensation in the drift region. All transient simulations were performed using Medicis mixed-mode simulation approach including self-heating. A higher epitaxial layer thickness eventually resulted in a higher avalanche ruggedness but also in higher on-state resistance. Thus, a trade-off exists.

PT-IGBT and freewheeling diode for 3.3 kV using lifetime control techniques and low-efficiency emitters

The adjustment of emitter efficiency by variation of doping profiles or application of lifetime control techniques such as irradiation of electrons and helium are two generally recognized concepts for the improvement of power device characteristics. In this work both concepts were studied by use of device simulation for the development of an IGBT and freewheeling diode chipset for 3.3 kV. Simulations were performed using an extended recombination model and recombination center data taken from measurements at different irradiated devices. Finally, this lead to the manufacturing of an IGBT using low-emitter efficiency and an irradiated freewheeling diode. The experimental results are in good accordance with the previously performed simulations and give evidence of the capabilities of present device simulation tools.

Parameters of radiation-induced centers for simulation of irradiated power devices

Irradiation techniques are widely used for carrier lifetime control, especially in power devices, because of their good reproducibility. Simulation of these devices is however lacking due to missing or incomplete recombination center data, despite the availability of suitable recombination models. In this work, we used center data estimated by DLTS and lifetime measurements for the simulation of electron radiated devices and compare the results with the measured device characteristics.

Comparison of different cell concepts for 1200 V NPT-IGBTs

IGBTs are relatively new power devices combining bipolar and unipolar properties. In this work we carried out theoretical investigations of IGBT cells with different concepts and properties using the two-dimensional device simulator ToSCA and the process simulation system DIOS. The investigations are done at three different cell types: a common planer gate cell with different p-base depths, a cell with double implanted emitter and a cell with a trench gate structure. For the realization of devices with low static losses and a high degree of ruggedness an advanced cell concept is necessary. For ruggedness modelling of the IGBTs the calculation of the short circuit current is used. It is shown, that the concept of IGBTs with double implanted emitter is a good alternative to the trench IGBT concept. An improvement of the short circuit behaviour of this device is possible in addition with lower static losses.