Dependence of inverter chain single-event cross sections on inverter spacing in 65 nm bulk CMOS technology

Single-event cross sections of four inverter chains, with uniform inverter spacing ranging from 120 nm to 4 μm, were experimentally measured and compared. These inverter chains were irradiated using a focused ion beam. Waveforms of responses were sensed using on-chip wide-bandwidth analog multiplexers. The outputs of the multiplexers drive the 50 Ω inputs of high speed real-time oscilloscopes used for recording the traces. Cross sections are examined for three different pulse height thresholds, for direct-hit waveforms as well as for waveforms propagated through the chain. We have observed that the cross section of tightly-spaced inverters is considerably smaller for both direct-hits and propagated single-event transients, and increases with increasing separation by a factor of 10 or more.