Microfabrication of lenses of a miniaturized electron column

A process for fully micro-machining electrostatic lenses is described. It is suited for batch processing of microlenses. Microlenses can be used for focusing electrons or ions in a microcolumn. In our case, they are made out of silicon membranes, which are used as electrodes, and insulating Pyrex spacers. Accurate patterning and alignment of the bore in the individual electrodes is achieved by electron beam lithography and a new registration method. The bores, which range from 1 to 100 @mm, are machined into the silicon by means of reactive ion etching. Vertical and smooth side walls with a residual roughness of less than 10 nm have been achieved.