Variations in Semiconductor Device Response in a Medium-Energy X-Ray Dose-Enhancing Environment

We have performed a series of experiments to investigate the response of semiconductor devices to medium-energy x-ray irradiation under conditions in which dose-enhancement effects are very important. We find that the response of MOS capacitors to the same "dose-enhanced" radiation depends not only on the increased dose, but also on the incident radiation spectra, device temperature and processing, and/or oxide thickness and electric field. In many cases, these dependencies cannot be explained simply in terms of existing knowledge of basic mechanisms of radiation effects on MOS devices (for example, electron-hole recombination and hole transport and trapping), or by present Monte Carlo electron/photon transport codes such as the Integrated Tiger Series (ITS). In addition, the response of semiconductor diodes to the "dose-enhanced" radiation appears to be qualitatively different from that of MOS capacitors, and differs markedly in value from the ITS code predictions. These results demonstrate that an improved understanding of semiconductor device response to "enhanced" radiation is needed to assure simulation fidelity of tests of devices to be used in dose-enhancing environments.