Cluster Impact SIMS
Original Publication Date: 1985-Aug-01
Included in the Prior Art Database: 2005-Feb-19
Improved Secondary Ion Mass Spectroscopy (SIMS) measurements are obtained when ionized clusters in the 100 - 1000 atom range and energies of 10 - 100 KeV are used as primary particles to sputter the surface being analyzed. A preferred method of generating the clustered primary beam uses a Liquid Metal Ion Source (LMIS) that is operated using a pulsed electric extraction field. An alternative method expands a metal vapor adiabatically and ionizes the clusters with an electron beam. The proposed method is particularly useful for the analysis of semiconductor structures, as it can be used to determine very shallow doping profiles; it yields reliable profile data already at 5 to 10 ˜ under the original surface, whereas the corresponding depth for conventional atomatic primary beams is of the order of 200 ˜.