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978-3-8439-2419-1, Reihe Elektrotechnik
Radiation Characterization of Highly Integrated NAND-Flash Memory Devices for Spaceborne Mass Storage Applications
330 Seiten, Dissertation Technische Universität Braunschweig (2015), Softcover, A5
The instruments on scientific spacecrafts produce high data rates up to several Gbit/s. Until the occasional data transmission to a ground station this data has to be stored temporarily in an on-board mass memory system.
NAND-Flash memories provide a high storage capacity, which is four times larger compared to SDRAM. The non-volatile storage enables a power-saving memory system, because the supply voltage can be switched off during times with no memory access. Radiation induced Single Event Functional Interrupts (SEFI) of the memory internal control circuitry can be removed by power cycling.
In the frame of this work the sensitivity of several NAND-Flash memories to space particle radiation is examined. Single Event Effects (SEE) are caused by single protons and heavier ions. The accumulative Total Dose (TID) effects are caused by a multitude of incident electrons, protons and heavier ions.
Devices with feature sizes of 51 nm and 25 nm are irradiated by protons, heavier ions and Co-60 γ photons. The cross sections at normal incidence for distributed data errors and for several SEFI types are determined, with special focus on Destructive Failures (DF).
For heavier ions the dependence of data errors on the angle of incidence is measured by means of a dedicated, remote controlled tilting setup. Multi Bit Errors (MBU) occur especially at slant incidence.
The annealing of data errors after exposure to ions as well as to Co-60 photons is studied.
The memory types differ substantially in the amount of their dose dependent growth of the standby current.
Periodic refresh of the memory contents shifts the TID induced effects to significantly higher dose levels.
The state of the art Micron 25 nm 16/32 Gbit device is more TID sensitive compared to the old Samsung 51 nm 8 Gbit device which is no more procurable.
No other memory technologies with a density comparable to NAND-Flash are on the horizon. Further progress in the density of planar Single Level Cell (SLC) NAND devices is no more expected. Instead, monolithic 3D approaches with several stacked active layers of less demanding feature size are promoted by several manufacturers. Concerning radiation sensitivity possibly this approach provides a path back to the radiation robustness of the 50 nm devices. Whether this promising approach is capable to overcome the present deadlock situation can be determined only by surveying radiation tests of early candidate devices.