Improved image resolution for wafer inspection tool using sub-200 nm wavelength (DUV light) light optical system

Bright field imaging systems are widely used for inline inspection tools to detect with high sensitivity defects on patterned wafers in semiconductor fabrication processes. We expect to extend this optical inspection method to 65 nm design rule and beyond by an improvement of resolving power using shorter wavelengths. To achieve this improvement, we evaluated inspection imaging characteristics with a DUV (sub-200nm, which is the shortest wavelength in practical use) light by reflectivity simulations and by experiments using a pilot POC (proof of concept) tool. Improvements in image contrast and wafer inspection capability were confirmed by the inspection experiments using test wafers having programmed defects. We confirmed that DUV light has enough reflectivity to inspect defects in principal semiconductor materials, and image contrast improves with increasing magnification when patterns are resolved.