Yield Test Structures Accelerate Learning

摘要

By employing large-area yield test structures early in the process development cycle, engineers rapidly identify the most significant yield detractors. Nick Atchison and Ron Ross of Silicon Systems (Santa Cruz, Calif.) developed new test structures they included in the reticle sets in the first few products using a 0.8 μm BICMOS process. The yield structures identified two main problems — poly-poly leakage caused by poly stringers and metal 2-metal 2 leakage caused by TiW stringers. The corrected problems accounted for 80% of the total yield improvement attained from first silicon testing to full production. Optimum yield was reached in six months.