Browse Prior Art Database

New Detector System for Scanning Electron Microscope

IP.com Disclosure Number: IPCOM000036797D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 42K

Publishing Venue

IBM

Related People

Via, GG: AUTHOR

Abstract

Scanning electron microscopes (SEMs) are widely used in the development and manufacturing of semiconductors. Of paramount importance is their use in the development of LSI, VLSI and ULSI chips, where dimensions of the order of submicrometer are observed.

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New Detector System for Scanning Electron Microscope

Scanning electron microscopes (SEMs) are widely used in the development and manufacturing of semiconductors. Of paramount importance is their use in the development of LSI, VLSI and ULSI chips, where dimensions of the order of submicrometer are observed.

A basic SEM tool is described to best understand the present disclosure. An electron emitter is maintained at a potential of a few kilovolts to generate a stream of electrons, which is directed and accelerated toward a perforated anode kept at a ground potential. The resulting energetic electron beam is passed first through a magnetic lens used as a condenser and then through a magnetic lens(es) where it is reduced to a finely defined beam of a few tens of angstroms in diameter. A set of scanning coils allow the finely defined beam to be "painted" over the surface to be studied. The energetic electrons of the scanning beam penetrate the material, and as a result, low energy (4-5 eV) electrons are liberated and leave the surface.

A grid-like static accelerator, kept at +500 V accelerates the secondary electrons toward a scintillator material. In the interaction of electrons with the scintillator, photons are emitted which follow a light pipe, hit a vacuum tight, optical window glass interface to strike finally the window of a photomultiplier. The signal out of the photomultiplier is used to Z modulate a CRT with consequent reconstruction of the image, in correspondence of the scanning of the sample by the primary electron beam.

Unfortunately, the use of a single detector in an SEM causes the loss of available secondaries not collected by a single detector, and the location of the single detector at an angle with respect to the scanning angle results in a shadowing signal from the sample where there are high topographical features.

This article presents a better detection system for an SEM. It defines a vastly improved detector system. The results obtained with the prototype a...