The Random Telegraph Signal Behavior of Intermittently Stuck Bits in SDRAMs

Probing the Nature of Intermittently Stuck Bits in Dynamic RAM Cells

“…1 reproduces Fig. 11 in [8] with the addition of dashed contours for the sticking thresholds of stuck bits with leakage currents of 0.1, 1 and 10 [arbitrary units] at 333 K). For a refresh frequency (i.e., the reciprocal of the refresh time interval) and device temperature at the sticking threshold, this may be expressed as:…”

“…These thresholds can be converted to actual levels of leakage current through the stuck bit by the following method. In our previous paper [8] it was observed experimentally that there is a linear relationship between the logarithm of the DRAM refresh frequency and the reciprocal of the absolute temperature for the sticking threshold of a stuck bit ( Fig. 1 reproduces Fig.…”

“…Fig. 4 of our previous paper [8]. However, it is also possible to compare this modeled leakage current profile directly with the real leakage current profiles shown in Figs.…”

“…2) comprised a version of the MBDA System for Testing Radiation Effects in Advanced Memories (STREAM) flash FPGA-based memory-testing system (see also [8]) modified with a pinch contact TSOP socket to hold the SDRAM memory sample in place in order to be able readily to change the device under test.…”

“…In dynamic RAM's, if the ambient temperature is high enough and the refresh duration sufficiently long, then these leaky cells may suffer discharge of their storage capacitances, hence appearing as stuck bits. It was shown last year that these leaky bits are attributable to displacement damage complexes produced by individual particle interactions or pairs of individual particle interactions and that the magnitude of leakage current through a complex can spontaneously flip between discrete levels, producing Intermittently Stuck Bits (ISB's) [8]. This paper describes advances in monitoring and modeling the intricate leakage current histories of these displacement damage complexes over the intervening year.…”