Ultra High Vacuum Scanning Electron Microscopy of Directly Deposited Metallic Films

Abstract

A basic scanning electron microscope of similar construction to that described by Pease and Nixon has been modified for ultra high vacuum by using a special stainless steel specimen chamber. The final aperture of the electron optical column is also the differential pumping aperture separating the lens and scan coil region from the specimen chamber. Recent further refinement has given a measured vacuum in the specimen region of 1 x 10-10 torr after baking and day to day operation at 10-8 torr. The specimen stage stability and the electron optical performance permit an electron probe size of 200-300 A at these vacuum levels. The main column is pumped to 10-6 torr.This improved vacuum performance is necessary for depositing and viewing thin metal films as there is no residual contamination and no effect of partial pressures of gases to influence the main reaction. Both silver and tin films have been deposited from halide compounds with a resulting metal thickness of about one micron giving reasonable conductivity. The substrate is silicon of integrated circuit quality.