Photoresist cross-sectioning with negligible damage using a dual-beam FIB-SEM: A high throughput method for profile imaging

摘要

Imaging of photoresist cross sections in a focused ion beam (FIB)-scanning electron microscope (SEM) is demonstrated with negligible damage. An in situ chromium sputtering technique is used to deposit metal on the site of interest, replacing the conventional and more damaging metal deposition by high energy ion decomposition of metal-organic precursors. Here, a high current ion beam is rastered over a small chromium target suspended over the wafer surface resulting in a less damaging metal deposition step. The subsequent resist critical dimensions measured via FIB-SEM are calibrated against profile measurements taken by critical dimension atomic force microscopy, implemented here as a reference measurement system (RMS) without the influence of beam exposure. The use of a nondamaging RMS allows an accurate measurement of resist damage during imaging. As a practical demonstration of this sputtering method, a 50 nm 1:1 line/space array in extreme ultraviolet photoresist is analyzed through focus and exposure.