Christoph Kadow

On the Origin of Thermal Runaway in a Trench Power MOSFET

In this paper, we investigate the origin of thermal runaway in the trench power MOSFET of a modern smart power IC technology. Experimental data on the temperature rise during power pulses show that the onset of thermal runaway depends on the biasing condition even if the power pulses have equal power dissipation. The beginning of thermal runaway in this work is denoted by the inflection point in the measured temperature data. For the experimental data points, the onset varies from 340 °C to 520 °C. Comparison of these experimental data with an analysis based on the stability factor shows very good agreement. The stability factor analysis demonstrates that, above the temperature compensation point (TCP), the driving force for thermal runaway is the thermally generated leakage current of the parasitic n-p-n bipolar transistor. The decrease of mobility and, hence, the MOS channel current above the TCP stabilizes the power MOSFET. In contrast, below the TCP, both the increase of the MOS channel current and the parasitic n-p-n bipolar transistor leakage current with temperature contribute to the thermal runaway.

Fabrication of trench isolation and trench power MOSFETs in a smart power IC Technology with a single trench unit process

We report on using a single trench unit process for the trench isolation and for the trench power MOSFET of a common-drain smart power IC technology. The trench power MOSFET has a maximum specific on-resistance, (Ron⋅A), below 50mΩ-mm2 and a typical breakdown voltage, Vbr, of 95V. The trench isolation provides well isolation up to 90V. Using a single trench unit process for both devices results in low process costs. In addition both power and logic areas of a chip benefit from the trench process.

Seebeck difference - temperature sensors integrated into smart power technologies

In this work, difference - temperature (ΔT) sensors based on the Seebeck effect integrated into a common drain smart power MOSFET technology are presented. The sensors generate a voltage signal proportional to the ΔT. The highest Seebeck coefficient measured was 0.92 mV/K. This result was achieved with a p - doped silicon and n+ - doped poly silicon Seebeck ΔT sensor. Power MOSFETs with embedded Seebeck ΔT sensors are, to our knowledge, demonstrated for the first time.