Heavy ion irradiation hardening study on 4kb arrays HfO$_2$-based OxRAM

Abstract : HfO$_2$ based OxRAM devices integrated in Back End Of Line (BEOL) of 130nm CMOS have been exposed to extreme irradiation conditions related to extensive journey in space, supernova or nuclear disaster exposure: 1.635 GeV Au ion energy and very high fluences, from 10$^9$ ions/cm² to 10$^{12}$ ions/cm². Single resistive devices as well as 4kbit 1T1R arrays have been studied, showing a very good resilience up to a fluence of 5.10$^{10}$ ions/cm². For higher fluences, the degradation of access transistors is identified as the main source for information loss. Without access transistor, single 1R devices were demonstrated to be functional even at the highest fluence of 10$^{12}$ ions/cm². TEM, EDX and nano diffraction analyses show no change in the HfO$_2$ material, as well as in the repartition of the element in the layers, whatever the fluence. These results demonstrate the OxRAM structure is resilient to extreme irradiation conditions.