Early Fault-Analysis Using In-Line Raman Spectroscopy Metrology

As semiconductor device dimensions scale down, process variation impact on reliability becomes increasingly severe. This trend stems from the high-reliability requirements typical for advanced system applications, the narrowing process margins and the high sensitivity of devices to material and dimensional variations. At the process level, many deviations from nominal conditions can degrade the devices' reliability. Examples are induced charge traps in the various types of memory cells, electrical performance inhibitors due to lattice defects or poor stress management and poor data retention due to contamination by killer elements. We claim that monitoring and correcting deviations throughout the fabrication process provides an effective approach for preventing reliability failures. By restricting deviations below specific threshold levels and screening out reliability and End Of line (EOL) related parameters, eventual device reliability can be safeguarded. This paper addresses the relationship between various process parameters and reliability, and reviews the enablers of preventive, early-detection inline metrology in the fab.