2 SEE Mechanisms

The primary single-event effect (SEE) events of interest in the SN54SLC8T245-SEP are the destructive single-event latch-up (SEL) and Single Event Transient (SET). From a risk or impact perspective, the occurrence of an SEL is potentially the most destructive SEE event and the biggest concern for space applications. The LBC7 process node was used for the SN54SLC8T245-SEP. CMOS circuitry introduces a potential for SEL susceptibility. SEL can occur if excess current injection caused by the passage of an energetic ion is high enough to trigger the formation of a parasitic cross-coupled PNP and NPN bipolar structure (formed between the p-sub and n-well and n+ and p+ contacts). The parasitic bipolar structure initiated by a single-event creates a high-conductance path (inducing a steady-state current that is typically orders-of-magnitude higher than the normal operating current) between power and ground that persists (is latched) until power is removed or until the device is destroyed by the high-current state. The process modifications applied for SEL-mitigation were sufficient as the SN54SLC8T245-SEP exhibited no SEL with heavy-ions up to an LET_EFF of 43 MeV-cm²/mg at a fluence of 10⁷ ions/cm² and a chip temperature of 125°C.

This study was performed to evaluate the SEL effects with a bias voltage of 3.6 V on V_CCA supply voltage. Heavy ions with LET_EFF = 43 MeV-cm²/mg were used to irradiate the devices. Flux of 10⁵ ions/s-cm² and fluence of 10⁷ ions/cm² were used during the exposure at 125°C temperature.

Figure 2-1 Functional Block Diagram of the SN54SLC8T245-SEP