Overlay and linewidth metrology on latent images

Is there enough contrast under white light illumination to perform automated metrology on latent or undeveloped photoresist images for control of the lithographic process? This would be an interesting option for the next generation photolithograpy cell. To accomplish this under full automation, several different operations must be carried out: global alignment which requires a coarse focus and pattern recognition operation at low optical magnification, pattern recognition and precision autofocus at high magnigication, and finally precision edge detection at high magnification all at repeatabilities acceptable to the industry. The first look answer is yes. Below we describe the experiments and data carried out on this question.