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978-3-8439-3723-8, Reihe Elektrotechnik
Radiation Characterization of Highly Integrated DDR3 SDRAM Devices for Spaceborne Mass Storage Applications
280 Seiten, Dissertation Technische Universität Braunschweig (2018), Softcover, A5
Scientific instruments aboard spacecraft generate large amounts of data, which has to be stored in mass memory for on-board processing or for later transmission to an Earth station. The spacecraft and its components are exposed to energetic particle radiation; however, radiation-hardened memory devices of suitable storage density are not available. This necessitates the use - and therefore radiation tests - of commodity memory devices.
Compared with its main competitor, NAND Flash, SDRAM offers a higher data rate (in particular for writing) and an unlimited number of write cycles. DDR3 is a type of SDRAM that is, at present, widely used as RAM for PCs and server systems. In the context of this work, the radiation sensitivity of eleven 2-Gbit and 4-Gbit device types (with a feature size between 30 nm and 50 nm) from five manufacturers has been tested, with the main focus on four contemporary 4-Gbit types.
Two classes of radiation effects are particularly relevant for SDRAM devices: single-event effects (SEE) and total-ionizing-dose (TID) effects. Single-events effects are caused by a single charged particle, while total-ionizing-dose effects result from the accumulated effect of many individual particles. In accordance with common test procedures, SEE tests have been performed with protons and heavier ions at particle accelerators, and TID tests with gamma rays from the radioactive decay of cobalt-60.
With respect to single-event effects, all tested device types have been found to be space-worthy: in particular, no radiation-induced latch-ups (SELs) or destructive events have been observed. However, single-event upsets (SEUs) and single-event functional interrupts (SEFIs) are common.
With respect to total-dose effects, some of the tested device types have been found to be very well suited for space applications, with only few data errors and minor current increase. With a tolerance to absorbed radiation dose that is several times higher than for NAND Flash, these device types are particular interesting for high-dose missions. However, certain access patterns can lead to data errors in radiation-impaired memory devices, and the memory controller for DDR3 SDRAM in a radiation environment must therefore be specifically tailored to avoid such effects.