TOWARD ACCURATE METROLOGY WITH SCANNING FORCE MICROSCOPES

Scanning force microscopes (SFMs) have become valuable instruments for inspection of surfaces on a submicron scale in the semiconductor indu stry. Their ability to track the position of a surface with an accurac y of the order of 1 nm opens the door to applications in micro- or nan ometrology. Standard SFMs, using a conical shaped tip, are being appli ed to measurements of the height or depth of shallow features, such as via holes or small lines and trenches, that cannot readily be charact erized by scanning electron microscopy or optical techniques. Recent t echnical developments of the SFM have provided new capabilities for ac curate measurement of the line and trench width using a flared tip and an improved scanning and tracking method for the tip. Laboratory test s as well as industrial tests have revealed that repeatability in meas uring critical dimensions approaches 1 nm. If careful attention is giv en to issues of calibration, particularly for the motion of the tip an d for dimensioning of the tip itself, SFM techniques may attain accura cies that approach their measurement precision. (C) 1995 American Vacu um Society.