M.O.S. Transistors with > 1 μm Thick Gate Oxide for Ionizing Radiation Dosimetry

Abstract

The effects of ionizing radiation on MOS transistors with gate oxide thickness up to 2 μm have been investigated. The major focus of workers in this area has been on the hardening techniques of technologies. On the other side, our goal is to use MOS devices to reach higher sensitivities in order to detect small amounts of dose. Therefore, sensitivity as well as temperature response in the mil-std range and stability of the dosimeters have been studied.

Prediction of the thermal annealing of thick oxide metal-oxide-semiconductor dosimeters irradiated in a harsh radiation environment

“…Applying the isochronal method on these data sets it is possible to estimate a room temperature recovery of ΔV gs less than 1 % over 10 4 hours (taken 1×10 7 sec -1 as factor of thermal acceleration 8 ). This prediction is in excellent agreement with experimental data presented in references 9,10 for the same devices exposed to tens of Gy in a pure ionizing radiation environment. The maximum neutron fluence that hits the device exposed to 10 Gy does not exceed 1.5×10 11 cm -2 .…”

Thick oxide MOS transistors for ionizing radiation dose measurement

“…However, when the dosemeter does not need to be portable, these working conditions can be of interest due to the high sensi tivity values which can be obtained, as shown in Figure 5 [8]. In addition, this figure shows that the sensitivity 1 varies linearly with the square of the oxide thickness in agreement with (1) Thus, by varying both the applied voltage on the gate and the insulator thickness during irradiation, the measurable dose range extends from 0.1 cGy [8] up to at least 10 6 Gy [5]. Furthermore, the possibility of integrating transis tors with different oxide thicknesses in the same package offers the complete dose range with one simple dosemeter.…”

“…Annealing of the post-irradiation trapped charge is increased at high temperatures [8,23]. This has been attributed to an increase in the thermal emission of holes from the trap centers to the Si0 2 valence band.…”

“…In fact, applying the processing requirement for a minimum annealing leads to 31% recovery at 100°C after 280 h [23] and 100% recovery after 1.5 h at 200°C [8].…”