Renesas has implemented a wafer-by-wafer low dose rate acceptance testing program to combat Enhanced Low Dose Rate Sensitivity (ELDRS), a phenomenon that threatens the performance of radiation-hardened semiconductors in space.
Understanding ELDRS and Its Impact
ELDRS causes increased sensitivity to radiation when exposure occurs at low dose rates, as in space. This leads to progressive performance degradation in semiconductors—something high-dose rate testing fails to predict, making low-dose rate protocols essential for reliability assurance.
Renesas’ Three-Phase ELDRS Testing Strategy
Legacy Product Testing
- Began in 2009
- 13 legacy parts tested under MIL-STD-883 Test Method 1019.7
- All devices passed 150krad (Si) low dose rate exposure
Wafer-by-Wafer Acceptance Testing
- Full production wafers tested at low dose rates
- Testing was done using a vault-type 60Co irradiator at Palm Bay
- Complements traditional high-dose rate tests
- Ensures Radiation Hardness Assurance (RHA)
New Product Characterization
- Focused on new parts like:
- Characterized at both high and low dose rates
- Based on 0.6µm BiCMOS process, found to be ELDRS-free
Palm Bay Low Dose Rate Irradiator Facility
Key Design Features:
- Structural Shielding:
- 36” walls, 48” roof of high-density concrete
- Reduces external dose rate by 10,000x
- Radiation Source:
- 50 Ci Cobalt-60 pop-up system
- Controlled exposure and safe storage
- Test Setup:
- Up to 64 DUT boards in spherical array
- Housed in PbAl spectrum hardening enclosures
- Safety Measures:
- Interlocked doors, emergency stop, UPS for secure operation
Facility Images:
External view of the completed low dose rate irradiator.
“Pop-up” source with surrounding test racks.
Impact on Space-Grade Components
Renesas’ approach significantly improves mission assurance by:
- Simulating real space radiation conditions during testing
- Identifying ELDRS-prone designs early
- Ensuring longevity and robustness of components before launch
This strategy contributes to safer, more reliable satellite and deep-space missions.
