Radiation hardness study of an APS CMOS particle tracker

The adequacy of Monolithic Active Pixel Sensors for charged particle tracking has been assessed, based on prototypes fabricated in 0.6, 0.35 and 0.25 μm CMOS processes. First radiation hardness studies of these prototypes are presented. Measurements were performed using a 30 MeV/c proton beam, a fast neutron beam from a nuclear reactor and a 10 keV X-ray generator as irradiation sources. The losses in the collected charge were measured after 5×10¹¹ protons/cm² as well as after a total fluence of 10¹² neutrons/cm². Moderate doses (hundreds of kRads) of X-ray photons induces an important increase of a leakage current, showing also limited effect on the collected charge. Test results are reviewed and new charge collecting radiation tolerant structures are proposed.