Effects of EUV Irradiation on Poly-Si SONOS NVM Devices

Abstract

The effects of extreme-ultraviolet (EUV)-irradiationinduced damage on the characteristics of a silicon-oxide-nitrideoxide-silicon (SONOS) memory device are investigated. After EUV irradiation, changes in the memory window and program/ erase speed indicate the generation of positive charges and new traps. Retention performance degrades after high-dose irradiation, which indicates that the tunneling layer is damaged. Endurance performance degrades severely because the damage in the blocking oxide results in serious electron back injection after cycling operations. These defects cannot be recovered after 600 • C annealing. It is recommended that in-process high-dose EUV irradiation on a SONOS stack after a front-end-of-line process should be avoided.Index Terms-Extreme ultraviolet lithography (EUVL), nonvolatile memory (NVM), radiation damage, silicon-oxide-nitrideoxide-silicon (SONOS) memory.

Observation of Extreme-Ultraviolet-Irradiation-Induced Damages on High-Dielectric-Constant Dielectrics

“…EUV irradiation during processing may result in reliability issue. Recently, we have reported the impact of EUV irradiation on a SONOS memory cell and observed that each layer in the ONO stack would be damaged by the EUV irradiation [4].…”