Oxidative cleaning method and apparatus for electron microscopes using an air plasma as an oxygen radical source
DCFirst Claim
1. A method for simultaneous cleaning of specimen chamber, specimen and stage for Scanning Electron Microscope, Transmission Electron Microscope, Scanning Electron Microprobe or other charged particle beam instruments to remove hydrocarbon contaminants by oxidation by generating oxygen radicals from air or other nitrogen/oxygen gas mixtures under vacuum conditions produced within said specimen chamber of said instruments, said method comprising the steps of:
- a) providing means for producing said oxygen radicals by a glow-discharge plasma;
b) providing means for temperature or power control of said glow-discharge plasma; and
c) using said temperature and power control to minimize ionization of nitrogen and maximize oxygen radical production in said plasma.
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Abstract
An improved method and apparatus are provided for cleaning the specimen and interior specimen chamber of Electron Microscopes, and similar electron beam instruments. The apparatus consists of a glow-discharge, oxygen-radical generator placed on a specimen chamber port with an excitation source to create a low-power glow-discharge plasma inside the generator. Air or other oxygen and nitrogen mixture is admitted to the generator at a pressure between 0.3 Torr and 5 Torr. The low power glow discharge is used to disassociate oxygen preferentially over nitrogen to create the oxygen radicals. The oxygen radicals then disperse by convection throughout the chamber to clean hydrocarbons from the surfaces of the chamber, stage and specimen by oxidation to CO and H2 O gases. The excitation power of the plasma is limited to limit the nitrogen ion production that destroys the oxygen radicals and to limit the projection of the electrically active plasma into the specimen chamber. The optical emission or color of the plasma is observed for the selection of the correct power level for maximum oxygen radical production.
81 Citations
14 Claims
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1. A method for simultaneous cleaning of specimen chamber, specimen and stage for Scanning Electron Microscope, Transmission Electron Microscope, Scanning Electron Microprobe or other charged particle beam instruments to remove hydrocarbon contaminants by oxidation by generating oxygen radicals from air or other nitrogen/oxygen gas mixtures under vacuum conditions produced within said specimen chamber of said instruments, said method comprising the steps of:
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a) providing means for producing said oxygen radicals by a glow-discharge plasma; b) providing means for temperature or power control of said glow-discharge plasma; and c) using said temperature and power control to minimize ionization of nitrogen and maximize oxygen radical production in said plasma. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. Apparatus for simultaneous cleaning of specimen chamber, specimen and stage for Scanning Electron Microscope, Analytical Electron Microscope, Scanning Electron Microprobe or other charged particle beam instruments to remove hydrocarbon contaminants by oxidation by generating oxygen radicals from air or other nitrogen/oxygen gas mixtures under vacuum conditions within said specimen chamber of said instruments, said apparatus comprising:
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a means for producing oxygen radicals by a glow-discharge plasma; and a means for temperature or power control of said glow-discharge plasma whereby within said plasma ionization of nitrogen can be minimized and the production of said oxygen radicals can be maximized. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification