Local and pseudo SELs observed in digital LSIs and their implication to SEL test method

Investigation of Current Spike Phenomena during Heavy Ion Irradiation of NAND Flash Memories

“…Although a total of 52 high current events were observed, none matched the 300-400 ms pulses described in [1,2]. Our results seem to be explained nicely by the mechanisms proposed by Shindou et al, [4], and we will discuss our results in light of these mechanisms. To shed more light on the mechanisms underlying high current events, pulsed laser experiments were conducted, using the Naval Research Laboratory (NRL) laser [5], to identify regions on the chip where high currents can be induced.…”

“…3, the duration of these events is more than three minutes for the longer one, and about 25 seconds for the shorter one. Again these are attributed to LSELs in Shindou et al [4]. The first high current event from Fig.…”

“…In Fig. 1, two high current events were observed, with stairstep structure characteristic of Localized Single Event Latchup (LSEL) [4]. The beam was turned off after the second high current event, at about t=300 sec.…”

“…The shortest newly observed events were nearly an order of magnitude longer. Forty-eight of the 52 events are rectangular, stair step waveforms which were identified in [4] as being caused by localized Single Event Latchup (SELs), where a small part of the circuit latches up. They observed that rest of the circuit remains fully functional, however, because sufficient bias voltage is maintained.…”

“…4, with baseline-to-baseline duration about 1 second. In Shindou et al [4] events similar to this are referred to as "pseudo-SELs", meaning the current increases rapidly, as in a true SEL, but the mechanism is contention on the data bus lines, rather than SEL. Bus contention results when two or more portions of the control logic are on at the same time, when they are not both supposed to be on, and they end up fighting for control.…”