Study of the correlation between the cutting edge current breakdown and the simulated lateral electrical field boundary in high resistivity silicon detectors with multi-guard ring structure

Abstract

High resistivity silicon detectors with a multi-guard ring structure (MGRS), after being subjected to laser cutting to various distances (L, from 10 /spl mu/m to 1000 /spl mu/m) from the outer most guard ring, have been used to investigate the effect of cutting edge current breakdown (CECB). The bias on the outer most guard ring at which CECB starts, or the edge breakdown voltage V/sub b/, increases monotonically with L. This result has been compared to the simulated lateral depletion depth (W/sub L/) from the outer most guard ring as a function of bias voltage V with very good correlation. For a given bias V, CECB occurs if W/sub L/ is larger than L, suggesting that current injects as soon as the electrical field reaches the cutting edge. These results indicate that damage caused by laser cutting is very much localized to the edge itself (within a few /spl mu/ms). The edge breakdown current can be separated from the bulk leakage current by grounding one of the guard rings. The advantage of using a MGRS to spread the electrical potential over a large distance to prevent possible high field breakdown was also simulated and discussed.