Comparison of n-side strip isolation methods for silicon sensors

Autoren: M. Valentan, T. Bergauer, M. Dragicevic, M. Friedl, E. Huemer, C. Irmler, W. Treberspurg

Precision experiments at electron-positron-colliders and b-factories demand high position resolution and low material budget for precise particle tracking. These requirements are fulfilled by thin double-sided silicon detectors (DSSDs). However, due to the low signals of thin sensors a careful sensor design is required in order to achieve high charge collection efficiency. In this paper we investigate the p-stop and the p-spray blocking method for strip isolation on the n-side of DSSDs with n-type bulk. We compare three different p-stop patterns: the common p-stop, the atoll p-stop and a combined p-stop pattern, whereas for every pattern four different geometric layouts are considered. Test sensors featuring these p-stop patterns and the p-spray blocking method were tested in a 120 GeV/c hadron beam at the Super Proton Synchrotron (SPS) at CERN (Geneva, Switzerland), where one variant of the atoll p-stop pattern performed best. The results of these tests are used to design the DSSDs for the Belle II experiment at KEK (Tsukuba, Japan).