Measurement of the linewidth of electrical test-structure reference features by automated phase-contrast image analysis

NIST, Sandia National Laboratories, and International SEMATECH are developing a new type of linewidth standard for calibrating Critical Dimension (CD) metrology instruments for lithographic process control. The standard reference feature is the bridge of an electrical linewidth test structure that is patterned in a monocrystalline silicon film. Phase-contrast images of the cross sections of a sample of the bridge features on each wafer, produced by High-Resolution Transmission-Electron Microscopy (HRTEM), are used to trace the measured electrical linewidths of the standard reference feature to the lattice constant of silicon. This paper describes the automated analysis of the phase-contrast images that was developed in order to minimize the cost and uncertainty of the linewidths of the standards.