reliability analysis chip
**Chip Reliability Analysis** is the **comprehensive evaluation of semiconductor failure mechanisms and their projected impact on product lifetime** — quantifying failure rates in FIT (Failures In Time, per billion device-hours), validating through accelerated stress testing, and ensuring that chips meet their specified lifetime targets (typically 10+ years) under worst-case operating conditions.
**Key Failure Mechanisms**
| Mechanism | Failure Mode | Acceleration Factor | Test |
|-----------|-------------|-------------------|------|
| TDDB | Gate oxide breakdown | Voltage, temperature | HTOL, TDDB |
| HCI | Vt shift, drive current loss | Voltage, frequency | HTOL |
| BTI (NBTI/PBTI) | Vt increase over time | Voltage, temperature | HTOL |
| EM (Electromigration) | Metal voids/opens | Current, temperature | EM stress |
| SM (Stress Migration) | Void in metal (no current) | Temperature cycling | Thermal storage |
| ESD | Oxide/junction damage | Voltage pulse | HBM, CDM, MM |
| Corrosion | Metal degradation | Moisture, bias | HAST, THB |
**Reliability Metrics**
- **FIT**: Failures per 10⁹ device-hours.
- Consumer target: < 100 FIT (< 1% failure in 10 years at typical use).
- Automotive target: < 10 FIT (< 0.1% failure in 15 years).
- Server target: < 50 FIT.
- **MTBF**: Mean Time Between Failures = 10⁹ / FIT (hours).
- 100 FIT → MTBF = 10 million hours (~1,142 years per device).
- Note: MTBF applies to a population, not individual devices.
**Qualification Test Suite (JEDEC Standards)**
| Test | Abbreviation | Conditions | Duration |
|------|-------------|-----------|----------|
| High Temp Operating Life | HTOL | 125°C, max Vdd, exercise | 1000 hours |
| HAST (Humidity Accel.) | HAST | 130°C, 85% RH, bias | 96-264 hours |
| Temperature Cycling | TC | -65 to 150°C | 500-1000 cycles |
| Electrostatic Discharge | ESD (HBM/CDM) | 2kV HBM, 500V CDM | Pass/fail |
| Latch-up | LU | 100 mA injection | Pass/fail |
| Early Life Failure Rate | ELFR | Burn-in at 125°C | 48-168 hours |
**Bathtub Curve**
- **Infant mortality** (early failures): Decreasing failure rate — caught by burn-in.
- **Useful life** (random failures): Constant low failure rate — FIT specification period.
- **Wearout** (end of life): Increasing failure rate — TDDB, EM, BTI accumulate.
- Goal: Ensure useful life period covers the entire product lifetime (10-15 years).
**Reliability Simulation**
- **MOSRA (Synopsys)**: Simulates BTI/HCI aging → predicts Vt shift and timing degradation over lifetime.
- **RelXpert (Cadence)**: Similar lifetime reliability simulation.
- Circuit timing with aging: Re-run STA with aged transistor models → verify timing still meets spec at end-of-life.
Chip reliability analysis is **the engineering discipline that ensures semiconductor products survive their intended use conditions** — rigorous accelerated testing and physics-based modeling provide the confidence that chips will function correctly for years to decades, a requirement that is non-negotiable for automotive, medical, and infrastructure applications.