Local Heating of Integrated MOSFET Dosimeter for Annealing Charge

The MOS dosimeters are used to keep track of the radiation dose for space, nuclear and medical industries, research laboratories and various applications like portable electronics and etc. MOSFET dosimeters constantly accumulate charge under the ionizing radiation effect, execute direct non-destructive readability of the dose information, have super-small sizes and low power consumption, can operate in a large range of ionizing radiation doses and can be integrated with other sensors and electronics. However, it is impossible to re-use the MOSFET dosimeters for their original purpose. In order to return the threshold voltage to its pre-irradiation value for dosimeter re-use, it is necessary to perform the accumulated charge annealing process. In the work the results of studying the structure of the integral elements, built-in into MOSFET dosimeter for local heating of the gate dielectric for the purpose of annealing the accumulated charge, created under the ionizing radiation, have been shown. The structure of such heating element has been using COMSOL Multiphysics. The heating element is the n -polysilicon gate of the MOSFET, through which electric current is passing. The test structures have been manufactured for 1.2um mixed analog-digital BICMOS technology. The temperature coefficient of resistance for the fabricated samples of the integrated resistors has been measured. It has been determined, that while the electric current passing through the integral element its heating and its resistance change in accordance with temperature coefficient of resistance. A comparison of the simulation results of the temperature dependence on the gate oxide thickness and the current runs through the heating element with the experimentally obtained data has been performed. The proposed method of local heating of the gate dielectric permits to achieve the temperatures of 700 °C order without destructive consequences for the structures and thus, to effectively anneal the accumulated charge in MOSFET dosimeter.
Dmitry V. Ryazantsev
SMC «Technological Center», Moscow, Russia
Evgeniy V. Kuznetsov
SMC «Technological Center», Moscow, Russia