The ability to accurately, quickly and automatically fingerprint the lenses of advanced lithography scanners has always been a dream for lithographers. This is truly necessary to understand error sources of ACLV, especially when the optical lithography is pushed into 130 nm regimes and beyond. This dream has become a reality at Texas Instruments with the help of scatterometry. This paper describes the development and characterization of the scatterometer based scanner lens testing technique (ScatterLith) and its application in 193 nm and 248 nm scanner lens fingerprinting. The entire procedure includes a full field exposure through focus in a micro stepping mode, scatterometer measurement of focus matrix, image field analysis and mapping of lens curvature, astigmatism, spherical aberration, line-through pitch analysis and ACLV analysis (i.e. across chip line width variation). ACLV has been directly correlated with image field deviation, lens aberration and illumination source errors. Examples are given to illustrate its applications in accurate focus monitoring with enhanced capability of dynamic image field and lens signature mapping for the latest ArF and KrF scanners used in manufacturing environment for 130nm node and beyond. Analysis of CD variation across a full scanner field is done through a step-by-step image field correction procedure. ACLV contribution of each image field error can be quantified separately. The final across slit CD signature is further analyzed against possible errors from illumination uniformity, illumination pupil fill, and higher order projection lens aberrations. High accuracy and short cycle time make this new technique a very effective tool for in-line real time monitoring and scanner qualification. Its fingerprinting capability also provides lithography engineers a comprehensive understanding of scanner performance for CD control and tool matching. Its extendibility to 90nm and beyond is particularly attractive for future development and manufacturing requirements.