Ellipsometric investigation of damage distribution in low energy boron implantation of silicon

As the scaling of silicon devices to 100 nm channel length requires the formation of ultra-shallow (< 60 nm) junctions, high depth resolution analytical techniques become necessary for the characterization of the dopant and damage distributions. In situ single wavelength Ellipsometric Etch Depth Profiling (EEDP) and non-destructive Variable Angle of incidence Spectroscopic Ellipsometry (VASE) have been used to obtain accurate and quantitative information on the depth profiles of radiation damage produced by low energy, room temperature ion implantation of B+ into Si. Implantation energy ranged from 250 eV to 10 keV and the dose was in the range 5 x 10(14) B+ cm(-2) to 5 x 10(15) B+ cm(-2). EEDP has been applied to damage depth profiling of low energy implanted silicon for the first time. The range and shape of the damage distributions obtained from optical model calculations are in good agreement with TRIM calculations for the energy range investigated. However, for the 10 keV implant, EEDP results unambiguously show the presence of a 6 nm thick amorphous silicon layer at the surface which is not predicted by TRIM. In the case of the 250 eV implant the presence of an amorphous Si surface layer can not be inferred from VASE data analysis although the existence of a 1 nm thick amorphous Si surface layer is indicated by EEDP.