Material Processing with Cluster Ion Beams

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An impact process of a cluster ion is far from monomer ion impact process. The peculiarity of the cluster ion collision on solid surfaces is the so-called "nonlinear phenomena". Unique bombardment effects have been reported for damage formation, sputtering and chemical reaction on solid surfaces. Many atoms impact on small surface area within femlo-second time scale. Therefore, a new interaction of each collision of the cluster constituent atoms with the surface atoms is expected. These dense collisions cause high yield of sputtering, surface smoothing, shallow implantation and high yield of secondary ion emission. The surface smoothing effect of cluster ions has been applied to many materials. We have studied irradiation effects on cluster ions, which are the aggregates of a few to thousands.Boron clusters with the size of ten are implanted to silicon. We have demonstrated shallow junction formation with so-called Decaboran ions. The irradiated region was investigated with EM(Transmission Electron Microscope) and RBIS(Rutherford Back scattering). The number of disordered atoms with cluster ion irradiation is an order of magnitude higher than that with monomer ion irradiation. The irradiated region can be completely amorphousized and recrystallized at low temperature without any damages. These phenomena are also found in the case of carbon cluster irradiation.