INSPECTION SYSTEM UTILIZING RETARDING FIELD BACK SCATTERED ELECTRON COLLECTION

A system for inspection of substrates and circuit devices employing a retarding field in an E-beam to reduce the incident beam energy to the crossover point at which minimum substrate charging occurs. This selectively separates backscattered electrons from secondary electrons emitted from the sample surface. An E-beam is columnated and directed through a bias plate and annular detector on a sample held at a negative bias with respect to the detector and the plate. The negative bias is selected so that the incident beam strikes the substrate at the crossover energy to permit collection of backscattered electrons. This selective detection generates a sharp image of the sample surface.