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United States Department of Agriculture

Agricultural Research Service

Title: Plasma-Etch Cleaning of Contaminated Strip Apertures: a Preliminary Report

Authors
item Droleskey, Robert
item Marlowe, Jack - HITACHI HIGH TECH AMERICA

Submitted to: Texas Society for Electron Microscopy Journal
Publication Type: Abstract Only
Publication Acceptance Date: April 4, 2003
Publication Date: N/A

Technical Abstract: Contamination of apertures in electron microscopes is initiated by the deposition of organic compounds on their surfaces within the microscope column. Sources of these organic compounds include vacuum oils used in the pumping system, gaskets and O-rings used to seal the vacuum system, greases used to lubricate O-rings, and finally the sample itself. Subsequent exposure of the deposited organic molecules to the electron beam results in the formation of a carbon film over the aperture surface. With time, accumulated contamination may hinder the ability of the user to compensate the microscope¿s condenser and objective lenses leading to either the replacement or cleaning of the contaminated aperture. The most traditional method utilized to clean strip apertures is to heat the strip to a cherry red hot state within a vacuum evaporator, or by direct heating with a propane torch. Heating strips to cherry red can lead to excessive heat build up which can distort the shape of the aperture strip as well as destroy welds used to hold multi-plate strips together. Subsequent to a recent TSM workshop on plasma-etch cleaning of SEM samples prior to observation in the microscope, we undertook to determine the suitability of using a plasma cleaner to remove the deposited carbon contamination layer from used condenser and objective strip apertures. Contaminated strip apertures were cleaned for 15-30 min in a Fischione Instruments plasma cleaner operating at 100 watts in a mixture of 75% argon and 25% oxygen. Prior to and after cleaning, strips were inspected and photographed using a conventional light microscope. Images generated from inspections before and after cleaning were compared for each aperture hole. Results indicate that plasma-etch cleaning effectively removed the contaminating carbon layers without distorting the aperture or affecting the dimensions of holes in the strip aperture. Further experiments will determine the minimal time and energy needed to effectively remove the contaminants from the surface of the aperture.

Last Modified: 12/27/2014
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