Radiation tolerance of ultra-thin PIN silicon detectors evaluated with a MeV proton microbeam

A focused MeV proton beam at the Lund Ion Beam Analysis Facility has been used to induce radiation damage in transmission semiconductor detectors. The damage alters the response of detectors and degrades their charge transport properties. In this work, the radiation tolerance of ultra-thin silicon PIN detectors was studied as a function of proton fluences and detector thickness using a scanning proton microprobe. The investigated detectors had thicknesses ranging between 6.5 and 22 mu m, and different selected regions of each detector were irradiated with fluence up to 2 x 10(15) protons/cm(2). The results show that the charge collection efficiency (CCE) decreases as a function of the proton fluence. Compared with non-irradiated regions, the CCE was above 94% at the lowest fluence of 2 x 10(12) protons/cm(2) for all the detectors studied. Degradation of the devices caused spectral peak shifting toward lower energies. The highest possible fluence of 2.55 MeV protons that could be used, causing only minor radiation damage, was 2 x 10(13) cm(-2) for the thinnest detectors (6.5 and 10 mu m) and 2 x 10(12) cm(-2) for the thickest detectors (15 and 22 mu m).