Effect of Ionizing Radiation on the Breakdown Voltage of Power MOSFETs

摘要

Vertical double-diffused (VD) metal-oxide-semiconductor (MOS) field-effect-transistor (FET), or VD MOSFET, is an awkward, intimidating name, but it succinctly describes the structure and operation of a very useful solid state device. First developed in the early 1980s, VD MOSFETs (also called power MOSFETs) have become widely used in the electronic industry due to their ability to switch large currents at high frequencies (10-100kHz) and because of their thermal ruggedness. VD MOSFETs are particularly useful in both space and military applications because they allow engineers to design power supplies that work at high frequencies; with higher power supply frequencies the size of the transformers, and therefore the weight of the systems, can be reduced significantly. Space-based systems operate in a cosmic radiation environment, and military radiation-hardness specifications must be satisfied; therefore, the effect of radiation on the operating characteristics of devices to be used in either application must be well known. The MOSFET structure is resistant to neutron damage at normally encountered fluences; however, they are sensitive to gamma radiation. Designers are primarily interested in knowing the effect of gamma radiation on the threshold voltage (VTH) and breakdown voltage (VBD) of MOSFETs. These two parameters are very important because, if they change, the behavior of a MOSFET in a circuit can change drastically.