Wafer Level Reliability
To fulfill the high requirements for a flexible, controlled production, X-FAB uses a modular qualification strategy that includes sophisticated reliability test methods at the wafer level. Because these Wafer Level Reliability (WLR) tests are conducted online in real-time on special test structures without affecting the rest of the wafer, they provide reliability information almost immediately, and thus allow the fast identification of process anomalies that could degrade long-term device reliability.
At X-FAB, WLR tests are performed at various stages of development and production. Several different state-of-the-art test methods are therefore employed, to invest and assess oxide integrity, metallization and transistor stability (hot carrier tests). This procedure guarantees the highest possible reliability of sensitive technology parts. The test selection required for each level of qualification depends on the different stages of technology changes (Technology Change Classification), in accordance with the JP-001 Foundry Process Qualification Guidelines.
The benefits of using WLR testing as an integral part of online production monitoring at multiple locations in the fab include:
- Real-time process monitoring
- Continuous process improvement
- Enhanced yields
- Lower rate of field failures
- Reduced testing costs
- Faster time-to-market for new products