A micromachined electron beam ion source

This paper presents the concept, the manufacturing details and the results of a micromachined ion source with the dimensions of only a few cubic millimeters. Since by scaling down a vacuum system the pressure increases at a constant Knudsen number. Usually filaments are used to generate electrons for electron beam ion sources. When the operation pressure increases to low vacuum the lifetime of a filament decreases unacceptably. For this reason, the ionising electrons are provided by a microwave-stimulated plasma. The aim of this concept is not only to scale down a macroscopic system but also to take advantage of the added features of a microsystem. Due to the electron source, the system operates at a relatively high pressure of about a few pascals, which principally simplifies the peripheral pumping system. The design of the ion source and its components are optimised with a simulation software tool. A technology known as the ‘poor menʹs LIGA,’ using the Epon SU-8 resist, is introduced into the manufacturing process. It eases the manufacturing of even complex microsystems. The complete system operates at a pressure of 100 Pa and the extractable ion current is about a few microamperes.