Chapter 4.9 - Preparation and Cleaning of Vacuum Surfaces

Abstract

This chapter focuses on the preparation and cleaning of vacuum surfaces. Surface preparation includes cleaning and surface modification. Cleaning means reducing the contamination level on the surface to an acceptable level for application of the vacuum environment. Surface modification can involve changing the surface morphology to be more rough or smooth, changing the chemical composition of the surface, changing the outgassing or outdiffusion properties of the material, or changing the mechanical properties of the surface. Surfaces should be cleaned as thoroughly as possible external to the vacuum system. External cleaning includes “gross cleaning” to remove large amounts of contaminants, often by removing some of the surface material, and “specific cleaning,” which is directed toward removing specific contaminants such as particulates or hydrocarbons. A clean processing environment and proper handling and storage after the external cleaning are important to minimizing recontamination of the cleaned surface before it is placed in the vacuum system. Some contaminants can be removed from surfaces by solvents that dissolve specific contaminants. Polar solvents such as water and water–alcohol mixtures are used to dissolve ionic materials that are the polar contaminates, and nonpolar solvents such as the chlorinated hydrocarbon solvents are used to remove nonpolar contaminates such as grease.