Small Particle Detection
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
The charging of small surface particulates by photoemission enables faster, more thorough inspection. In the schematic diagram of Fig. 1, light 1 from an ultraviolet pulsed laser charges particles 2 on work surface 3 by flood illumina tion. Since the particles have relatively high electrical resistance contacts with the surface, indicated by resistors 4, the photoelectron currents emitted from the particles produce differential charging with respect to the surface. Scanning electron microscopy (SEM) will show the particles clearly because of the charging contrast. To avoid the serial data collection and large quantities of data for high resolution during SEM scanning, an alternative arrangement (Fig. 2) can be used. Here, particles 2 and surface 3 are subjected to flood illumination, as in Fig. 1.