Critical-Dimension Measurement using Multi-Angle-Scanning Method in Atomic Force Microscope

We have developed a new critical dimension (CD) measurement technique using atomic force microscope (AFM) which can measure width-dimensions and examine sidewall-shapes of fine patterns on a wafer. The technique employs a flared-type tip in combination with digital probing and multi-angle scanning mechanism that allows the tip to trace the sidewalls on both sides of a feature (or trench) by making physical contacts with the sidewall surface. First, by using finite element method (FEM) we analyzed deformation of the tip and cantilever to compensate errors caused by the deformation. To verify our compensation method we measured quartz reference patterns either with perpendicular sidewalls or undercuts. In this paper we will describe the applications and usefulness of this multi-angle operation and show some measurement results of ArF resist patterns with 200 nm width and 400 nm depth that were obtained with a flared tip of 120 nm diameter.