The Phenomenon of Electron Rollout for Energy Deposition and Defect Generation in Irradiated MOS Devices

Energy deposition and defect generation in the gate oxides of MOS devices irradiated with 10 keV x-rays are analyzed. Particular attention is given to the role of secondary electrons produced by inelastic scattering and plasmon decay processes. It is shown that more than 50% of x-ray generated holes are produced by electrons of less than 100 eV. A mechanism, "electron rollout", which reduces hole generation in thin gate oxides is discussed. A concept of the hole production enhancement factor is introduced as an refinement of the commonly used absorbed dose enhancement factor. Results of calculations of enhancement factors based on these ideas are presented. These revised enhancement factors are about 20% smaller than previously calculated absorbed dose enhancement factors for oxides with thicknesses in the neighborhood of 50 nm.