Resistance to radiation of a 0.8 μm CMOS VLSI readout of instrumentation for accelerators used in tumor therapy

This paper shows the results of irradiations with photons and neutrons of a Very Large Scale Integration (VLSI) CMOS AMS 0.8μm chip used in medical physics applications. It has been designed as readout of dosimeters and monitor chambers used on electron/photon and proton/carbon ions for tumor therapy. The chip is located close to the detectors and it is thus used in a radioactive environment. We have performed measurements on 30 MV X-rays, fast and thermal neutrons. The chip behaves well (i.e. the gain variations are below 1%) up to X- ray doses of 75 krad and a total fast neutron number of 4*1012. This allows the use of the chip over several years (>5) without performance modifications. It has to be noticed that in real life the dose rates are much lower than during the tests, allowing a self-repairing of the chip with annealing. No Single Event Effect was observed up to 1010 neutrons. (authors)