Copper process control with picosecond ultrasonic technology: A study

Copper topography control during the IC fabrication process is a critical process step as it maintains global planarity across the wafer. Die to die variations in Cu thickness occur during copper deposition and removal process at various metal levels. In this work, the challenges associated with obtaining good process control of Cu thickness using Metapulse tools is discussed. The stability and accuracy of the measurement recipe is analyzed and improved. It is seen that these improvements are directly correlated to reduced thickness variation thereby enabling tighter process control in advanced technologies.