Thermal and electrical emulation of power semiconductor devices

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Dr. Ress Sándor László
Department of Electron Devices

Power semiconductors play a critical role in a world depending on electricity, as they are responsible for controlling the current flow.

Nowadays, as electronics industry is developing rapidly, semiconductor devices are becoming smaller and smaller, causing a significant increase in the dissipation per unit surface area. Problems concerning heat should not be swept under the carpet, as the characteristic of semiconductor devices is temperature dependent – meaning, in case of a temperature change, the operation of the device alters. This may lead to the improper functioning of the circuit, or, due to the excessive dissipation, even the decay of the device.

To enhance reliability, thermal effects should be taken into consideration even in the stage of development. Thermal transient measurement is a widely known method for examining the electrothermal behaviour of semiconductor devices. For testing reliability, power cycling is used.

For my thesis, I designed a device which is able to support the hardware and software development of the equipments suitable for the aforementioned measurements. The aim of the designed device is to emulate the voltage- and thus, the temperature change of the electrically excited semiconductor. In this way, there is no need to configure a measurement layout during the development of the equipments mentioned above; also, measurement on an actual device becomes unnecessary. With the help of the emulator, the thermal behaviour of any device that has been measured before can be examined; also, the analysis can be repeated unlimitedly.

To ensure the quality control of the measuring equipments, several thermal transient measurements are performed on a device. During these tests, characteristics of the device may change. This might prove to be problematic, because it must be determined if the change in the measurement is a result of a failure of the measuring equipment or of the measured device. In contrast, the emulator always performs the same behaviour, making the procedure of quality control faster and more simple.

I also introduce my self-developed real-time model which is suitable for emulating any kind of semiconductor device, based on its concentrated RC-parameter model. By changing the RC-members that make up the model, examining the decay of the device can be implemented real-time.

In my thesis, I present the steps of developing the emulator and the procedure established for modeling the degradation.


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