Total Ionizing Dose Effects on Floating Gate Structures. Preliminary Results.

The design and characterization of an ionizing radiation sensor for radiotherapy applications based on floating gate structures are presented. The devices were fabricated in a commercial CMOS process, and the floating gate was extended over field oxide in order to improve the radiation sensitivity. Such devices are a useful tool for studying the total dose effects on floating gate structures. The sensor is provided with an injection electrode in order to manipulate the charge stored in the floating gate, allowing not only to set different charge conditions for a complete characterization, but also to restore the floating gate to a desired state after the charge was neutralized by radiation. The devices response to ionizing radiation was studied, showing that sensitivity increases as more charge is stored in the floating gate. The experimental results help to improve the modeling of total ionizing dose effects on floating gate structures and predict their degradation. Preliminary results show that the charge manipulation was successful in several samples, and also experimental results show good agreement with the expected theoretical sensitivity.