PureB multi-guard ring structures for detector applications

Abstract

The breakdown voltage is an important parameter in designing X-ray detectors such as silicon drift detectors (SDDs). In SDDs the complete thickness of the wafer has to be depleted to enable the detection of different energies of X-rays. A high voltage is required to have a fully depleted region while keeping the leakage current low. Multi-guard ring structures are designed to meet both a low leakage current and a high breakdown voltage using deposited PureB layers. To obtain a low leakage current, PureB layers were used. In multi-guard ring structures, parameters such as gap width, number of the rings and overlap of the metal field plate with the oxide have been designed to obtain higher breakdown voltage. Parameters such as gap size, oxide charge, bulk doping concentration and field plate design have an influence on the potential distribution of the guard rings. The designed structure works up to the limit of the measurement systems (1100 V) with very low leakage current in the range of 1.5-3 nA/cm² for the detector.