COMPARISON OF SINGLE EVENT PHENOMENA FOR FRONT BACK IRRADIATIONS/

For devices irradiated from the front and the back, where ions have th e same LET in the sensitive volumes, the SEU sensitivities and charge collection spectra are different. A specific test setup has been devel oped to make precise measurements of both collected charge and SEU in CMOS SRAMs. We present a set of new data and discuss the possible expe rimental artifacts that could affect these measurements. In all the ca ses, the device is more sensitive when irradiated from the back than f rom the front. This phenomenon seems related to energy transfer mechan isms from the ion to the material target, with secondary particles fro m both electronic and nuclear reactions being forward emitted. This ef fect may influence to net sensitivity of scaled down devices, with sha llow sensitive layers, and heavy metal interconnects.