Influence of the DLC Passivation Conductivity on the Performance of Silicon High-Power Diodes Over an Extended Temperature Range

L Balestra,E Gnani,S Reggiani,J Vobecky,J Dobrzynska,A Gnudi

doi:10.1109/jeds.2021.3073232

L Balestra, E Gnani + Show 4 more

Open Access

https://doi.org/10.1109/jeds.2021.3073232

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Abstract

The diamond-like carbon (DLC) is important for passivation of junction termination in high power devices due to its excellent electrical, mechanical, and thermal properties. While the role of conductivity and polarization of the DLC layer on the blocking capability of a p-n junction has been explained recently, the thermal behavior still needs to be addressed. For this purpose, the diode leakage current was measured on large area power diodes with negative bevel coated by the DLC in a typical industrial range between 300 and 413 K. An unusual deviation from the expected Arrhenius law was experimentally observed. A predictive TCAD model, which incorporates the effect of the DLC layer, has been developed to study the impact of the DLC layer parameters on diode thermal performance. Both the electrostatic features and charge transport mechanisms through and along the DLC/Silicon interface have been modeled over a wide range of temperatures. Different DLC/Silicon doping combinations have been analyzed to explain the main effects determining the temperature dependence of diode leakage current and breakdown voltage. A complete validation of the TCAD approach has been achieved.

Highlights

The increase of maximal allowed junction temperature Tjmax of power semiconductors while preserving long-term blocking stability belongs to one of three methods to increase the output current and hereby the efficiency of high-power converters
The parameter determining the blocking stability and hereby the Tjmax is the leakage current IOFF generated in the active area and at junction termination (JT)
The parameter determining the efficiency of device design is the size of the JT relative to the active area

Summary

Introduction

The increase of maximal allowed junction temperature Tjmax of power semiconductors while preserving long-term blocking stability belongs to one of three methods to increase the output current and hereby the efficiency of high-power converters. The parameter determining the blocking stability and hereby the Tjmax is the leakage current IOFF generated in the active area and at junction termination (JT). What can further improve the situation is an optimized behavior of the JT in terms of robustness and area consumption, which depends on the surface passivation material and its processing.In addition to the electrostatic effect of the JT geometry and doping, if a semiinsulating passivation layer is used on top of the junction termination of the diode, IOFF (T) is influenced by the conductivity features of the passivation material leading to a modulation of the leakage current. A physically-based model of the passivation layer is needed for optimization of the

Methods

Conclusion