Ion sources for dry etching: Aspects of reactive ion beam etching for Si technology (invited)a)

Aspects of ion beam sources are treated which emerge from their use for reactive ion beam etching (RIBE) in silicon VLSI technology. As a basis for this treatment, the requirements for dry etching for VLSI are elaborated, as well as the consequences of these requirements for ion beam sources to be used for such technology. Practical experience with two types of ion beam sources for this application are highlighted, a classical Kaufman source and a first-generation ECR source. Aspects relevant for microfabrication related to grid optics, and the use of reactive gases, are discussed. Most important in this context are the internal microdivergence of an ion beam and the fragmentation of molecular gases taking place in the source and the ion beam as well. The consequence for potential application of RIBE for micropatterning must be to characterize sources by measuring their energy- and angle-resolved particle fluxes to the wafer.