Analyzing the State of Health of Diode Layers by using Structure Functions

The non-destructive quantification of a semiconductors’ state of health is difficult and extensive. The presented paper explains a precise, non-destructive analysis method for power diodes, which illustrates the state of health for each layer. The method is based on thermal impedance spectroscopy which analyzes the thermal transient, especially the cooling curve. By describing the thermal stack as an electrical equivalent circuit, thermal resistance and capacitance of each layer can be determined. Comparing these with the initial state, deviations can be detected.With this method, the diodes health can be monitored to detect critical layers long before the diode fails. Quality issues can be detected as well. Up to now, this is mainly done with expensive and time consuming end-of-life tests or micrographs. These disadvantages can be improved upon with this method. Additionally, this paper describes the application of this method for the evaluation of diodes which can predict if the desired reliability is achieved.