Ultralow Power Ionizing Dose Sensor Based on Complementary Fully Depleted MOS Transistors for Radiotherapy Application

We evaluate the use of thick buried oxide (BOX) of fully depleted silicon-on-insulator (FD-SOI) transistors for total ionizing dose (TID) measurements in a radiotherapy application. The devices were fabricated by a custom process at Université Catholique de Leuven (UCL) that allows one to make accumulation mode pMOS transistors and inversion mode nMOS transistors. We characterized the temperature behavior of these devices and the response under X-ray irradiation produced by an Elekta radiotherapy linear accelerator and compared the obtained dose sensitivity with other published works. Taking advantage of these devices, an ultralow power MOS ionizing dose sensor or MOS dosimeter with inherent temperature compensation is presented. This dosimeter achieved a sensitivity of 154 mV/Gy with a temperature error factor of 13 mGy/°C and a current consumption below 1 nA.