reliability testing

**Semiconductor Reliability** — ensuring chips function correctly over their intended lifetime under real-world operating conditions. **Key Failure Mechanisms** - **Electromigration (EM)**: Current flow physically moves metal atoms in interconnects, eventually causing open circuits. Worse at high current density and temperature - **TDDB (Time-Dependent Dielectric Breakdown)**: Gate oxide degrades over time under electric field stress until it shorts - **HCI (Hot Carrier Injection)**: High-energy carriers get trapped in gate oxide, shifting threshold voltage - **NBTI (Negative Bias Temperature Instability)**: PMOS transistor degradation under negative gate bias. Major concern for scaled devices - **BTI**: Both NBTI and PBTI affect threshold voltage over time **Testing Methods** - **Accelerated Life Testing**: Elevated temperature and voltage to compress years into hours. Use Arrhenius equation to extrapolate - **Burn-In**: Stress chips at high temp/voltage before shipping to weed out infant mortality failures - **HTOL (High Temperature Operating Life)**: 1000+ hours at 125C to verify lifetime **Metrics** - **FIT (Failures In Time)**: Failures per billion device-hours. Target: < 10 FIT for automotive - **MTBF**: Mean Time Between Failures **Reliability** is especially critical for automotive (10-15 year lifetime) and aerospace applications.