Application of nano-cluster ion beam to surface smoothening, etching, and ultra-shallow junction formation

Abstract

Gas clusters of a few nm are generated by adiabatic expansion through a Laval nozzle. Time-of-flight measurement is used to calculate the mean size of the generated clusters, confirmed by the isolated-impact induced hillocks, which are a few tells to a few hundreds nm in size from the measurement of all atomic force microscope (AFM). CO2 cluster ions are irradiated on Si wafers at an acceleration voltage of 25 kV to 50 kV and a flux of 10(9)/cm(2) s with variation of the ion dosage from 10(10)/cm(2) to 10(13)/cm(2). Through this isolated cluster ions impact, all interaction mechanism between the cluster ions and the solid surfaces is suggested to be composed of three steps: surface embossment. surface sputtering and smoothening, and surface etching. When cluster ions are impinged on indium tin oxide (ITO) on glass substrates at the acceleration voltage of 50 kV, the surface roughness of ITO is changed from 1.3 nm to 0.9 nm after irradiation of the cluster ions at the ion dosage of 5 x 10(14)/cm(2). Also the cluster ions are irradiated on a stress-released Si3N2 film, one of the base materials for microelectromechanical systems (MEMS), with deposited Cr metal as a metal mask. After irradiation of the cluster ions at the ion dosage of 4 x 10(14)/cm(2), the surface roughness of the Si3N4 film etched as deep as 30 nm is changed from 1.1 nm to 0.16 nm. Decaborane (B10H14) ions are implanted on n-type Si wafers at the acceleration voltage of 5 kV to 15 kV and the implanted wafers are annealed for 10 s in N-2 at 800 1000degreesC. Front a depth profile by a secondary ion mass spectroscope (SIMS). B-11 is not diffused deeper than 40 nm after rapid thermal annealing (RTA) at 900degreesC. All the samples showed higher hole concentration than 5x10(19)/cm(2) and lower leakage current density than 10(-4) A/cm(2). This means that decaborane ion implantation call be used to make ultra-shallow p(+)-n junctions little transient enhanced diffusion (TED).