Phi-scatterometry for integrated linewidth and process control in DRAM manufacturing

A cost-effective scatterometry method is presented that is suited for integrated pattern and process control and is valuable as a supplement to conventional scanning electron microscopes. The phi-scatterometry procedure is carried out directly on periodic functional patterns instead of using additional test structures. Time-consuming simulations of diffraction effects are not required. The measurement results are evaluated by neural networks performing classifications of pattern and process parameters. Thereby, fast fault detection and immediate process control are achieved. The measurements were performed on a 300-mm wafer with systematically varied focus and exposure as well as on production lots, both with DRAM patterns featuring trenches in two dimensions. A phi-scatterometry prototype was built which is suited for flexible mobile metrology in 300-mm production environments.