Browse Prior Art Database

Small Particle Detection

IP.com Disclosure Number: IPCOM000039031D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Cooper, DW: AUTHOR [+2]

Abstract

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.

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Small Particle Detection

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. However, direct photoelectrons as well as secondary electrons emitted from the surface are accelerated and focused by electron lens 5 onto fluorescent layer 6 on high voltage screen 7. Where charged particles 2 retard or capture electrons, dark regions will be observed on the screen. This two-dimensional pixel approach enables more efficient gathering of data for inspection.

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