A new scanning capacitance microscope (SCM) mode was implemented by using an atomic force microscope (AFM) operated in intermittent contact and by measuring the tip-to-sample capacitance change at the tip vibration frequency. The intermittent-contact-mode SCM was able to image and determine the overlay separation of metal lines buried under an 1 [mu]m thick, planarized dielectric layer. Modeling of the intermittent-contact SCM signal across buried metal lines was consistent with the experimental results. This hybrid intermittent-contact AFM and SCM has the potential to measure the lithographic overlay between metal lines located at consecutive levels beneath dielectric layers in an integrated circuit.
Citation: Applied Physics Letters
Pub Type: Journals
atomic force microscopy, buried line imaging, overlay metrology