A new trench-field-plate high-voltage power MOSFET

Abstract

Power MOSFETs are widely used in power electronic systems. For high voltage power MOSFETs, conventional power MOSFETs suffer from high on-state conduction loss due to the trade-off relationship between specific on-resistance (R_on,sp) and breakdown voltage (BV). In this thesis, a new trench-field-plate (TFP) high-voltage power MOSFET is proposed and analyzed. The device features benzocyclobutene (BCB) dielectric in the sidewall of deep trenches in the drift region and a sloped field plate (FP) inside each of the trenches. The TFP structure employed in the drift region modulates the electric field in the off-state, resulting in a higher breakdown voltage than that of the conventional power MOSFETs. Simulation results show that the specific on-resistance of the TFP power MOSFET is approximately one third that of the conventional power MOSFET and about 50% lower than that of the silicon limit for the same breakdown voltage. In addition, compared with super-junction devices, the TFP power MOSFET is able to provide better reverse recovery characteristics, including reduction in peak reverse recovery current (I_RRM) and reverse recovery charge (Q_RR) by 24% and 37%, respectively. A PiN diode employing the TFP structure is used to verify the voltage blocking capability of the TFP power MOSFET. Both the TFP PiN diode and the conventional PiN diode are fabricated on the same substrate for comparison. The test results show that the breakdown voltage of the TFP PiN diode (522 V) is 2.3 times that of the conventional PiN diode (220 V). The results demonstrate that the TFP structure can modulate the electric field distribution and hence increase the breakdown voltage. And a TFP PiN diode has been tested at an elevated temperature of 150 ℃, it is found that the breakdown voltage of the TFP PiN diode has increased from 510 V to 536 V. In addition, liquid crystal measurement results show that the breakdown of the TFP PiN diode occurs at the active region.

Date of Award	2020
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology