Ion beam induced charge microscopy studies of power diodes

Abstract

Ion beam induced charge microscopy (IBIC microscopy) has been established recently as an analytical tool for the characterization of various types of semiconductor devices. In this paper the potential of IBIC microscopy for the analysis of deeply buried structures of high power devices under biases of more than 2 kV is discussed. Such data are useful in the design process of high power devices because excessive fields at device edge regions or within protection elements (e.g. field ring structures) can be avoided. Since charge collection efficiency within depleted pn junctions is typically 100% for IBIC analysis, the contrast due to E-field variations within the large depletion regions of high power devices is limited. Here we will introduce a new approach for enhancing this contrast by using the temporal information from the IBIC signals gained with a transient IBIC set-up. Simulations and experimental data will be compared to evaluate the suitability of the new approach. The device used here is a high voltage diode with a field ring structure which was analysed using a 2 MeV proton beam.