Effects of heavy ion exposure on nanocrystal nonvolatile memory

Radiation Hardness of Flash and Nanoparticle Memories

“…NCMs are expected to have better resistance to ionizing radiation: being able to retain information with only a residual fraction of nanocrystals charged, these devices should be quite immune to radiation-induced leakage current, RILC (Larcher et al, 1999;Scarpa et al, 1997;Ceschia et al, 2000 ;Oldham et al, 2005), and they may in principle exhibit high resistance to both single event (SEE) and total ionizing dose (TID) effects. While some works already investigated the effect of ionizing radiation on FG Flash memories, until now, few works have investigated this issue in NC NVMs and will be briefly reviewed in the next.…”

“…Oldham (Oldham et al, 2005) reported on the exposition to heavy ion bombardment and total ionizing dose of advanced nanocrystal nonvolatile memories. The test chips were experimental 4Mb Flash EEPROM memories fabricated using 0.13 μm design rules, with NAND architecture (Freescale).…”

Radiation Tolerance of Nanocrystal-Based Flash Memory Arrays Against Heavy Ion Irradiation

“…The samples were irradiated with Br ions ( 241 MeV, 38.6 MeV cm mg ) at wafer level, which is the most likely operating condition for non-volatile memories [19]. In fact, non-volatile memory cells are often left unbiased while being sporadically read or programmed.…”

“…Such structures permitted the first-order evaluation of the radiation response of memory cells, but for a more comprehensive analysis, we need more complex structures, such as addressable arrays, which permit the estimation of the exact number of failing cells, the actual threshold voltage shift of the failing cells, and, above all, it enables close tracking of changes in the characteristics of each cell in the array. The first work on prototype NCM intended to evaluate different cell designs and processes [19] presented results on nanocrystal memories, favorably comparing with those on currently available commercial flash technology, and indicating a promising future for NCM even for space and military applications. In [20] and [21] we showed promising results regarding NCM in terms of both single event and total irradiated dose effects, highlighting that NCM's can tolerate radiation doses as high as several Mrad's.…”

“…In the last years it has been demonstrated that NCMs have a very good potential in retaining the electric charge within the nanocrystal layer after irradiation [19]- [21]. However, most of these results have been obtained by studying the "average" characteristics of CAST (Cell Array Stress Test) structures, featuring 256 kbit cells with parallel connection.…”