Three-dimensional metrology with side-wall measurement using tilt-scanning operation in digital probing AFM

We have developed a new measurement techniques employing digital probing with AFM (Atomic Force Microscope) that can examine sidewalls of fine patterns. This new technique employs digital probing operations, such sample-tilt step-in operation, tilt-step-in operation with a sharpened tilted tip, and multi-angle step-in operation with a flared tip. Firstly, we examined the validity of digital probing operation using a carbon nanotube (CNT) tip, showing the measurement repeatability of approximately 1 nm (3 sigma) on a fine trench pattern with 50 nm width and 300 nm depth. After the slip calculation between the tilted-tip and the sidewall for the new sidewall measurement technique, we measured a perpendicular reference sidewall with two types of operations, namely, tilt-step-in and multi-angle step-in operations. We then obtained 3D images of ArF resist patterns that involved measurement of sidewall surface roughness. Finally, we demonstrated a possibility of extending the technique for measuring denser trench patterns by using sample-tilt method and a tilted CNT tip.