Abstract
Full waveforms of single-event transients (SETs) in inverter chains were measured under focused heavy-ion microbeam irradiation. Inverter chains of varying spacings were irradiated with 48Ca and 197Au ions. The influence of changing the supply voltage from subthreshold to nominal level on SET forming and propagation was investigated, and the role of charge sharing is discussed. Key factors that influence SET widths and cross sections are identified across the applied range of supply voltages. A simple method is presented for estimating average SET widths at decreased supply voltages, and is based on the SET width measurements at nominal supply voltage, transistor-level simulations, and extracted circuit parameters. The proposed method matches well with the measured data.
Highlights
A S TECHNOLOGY progress pushes the scaling of integrated circuits further, the increased transistor density along with smaller operating voltages has led to increased susceptibility to single-event effects (SEEs)
An energetic particle passing through silicon close to a circuit node can induce a single-event transient (SET), which can propagate to a memory element, and create a single-event upset (SEU)
At lower VDD values, where transistors are operating in the nearthreshold or subthreshold regions, a more drastic increase of pulse widths can be seen. As it can be concluded from typical SET waveforms across different VDD values shown in Fig. 3, the pulsewidth of a typical SET is determined by three components: 1) a fast leading edge, which is independent of the circuit speed; 2) a plateau, which depends on the strike location, ion energy, and LET; and 3) a trailing edge, which gets slower with decreasing VDD [4], [6]
Summary
A S TECHNOLOGY progress pushes the scaling of integrated circuits further, the increased transistor density along with smaller operating voltages has led to increased susceptibility to single-event effects (SEEs). Since high transistor density and low supply voltage are very desirable for cost and energy efficient designs, it is important to understand how these properties affect the SEE sensitivity of circuits. Bringing sensitive nodes closer together has been shown to increase SEU rate in conventional radiation-hardened circuits, such as dual-interlocked cell (DICE) flip-flop, due to a charge sharing effect [1], [2]. Even small fluctuations below the nominal supply voltage were shown to cause considerable increase in the SET pulse widths, and in the SEU rate [6]. Even though struck nodes show increase in produced SET pulse widths when the supply voltage is decreased, Qin et al [12] suggest that pulse widths of propagated SETs may decrease, thanks to the charge sharing effect
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