Probing high‐energy ion‐implanted silicon by micro‐Raman spectroscopy

Abstract

The effect of ion implantation (4 MeV12C2+, 5 MeV16O2+, and 8 MeV28Si2+) on [110] silicon wafers in channeling and random orientation is investigated by micro‐Raman spectroscopy. The profiles were measured using Scanning Electron Microscope (SEM) showing that the ions were penetrating deeper inside the wafer in the channeling case creating a 1–2 µm wide strongly modified region and agreeing with the d‐nuclear reaction analysis measurements. Micro‐Raman spectroscopy was employed for the assessment of the lattice damage, probing the side surface of the cleaved wafers at submicron step. The phonon modifications show strong lattice distortions in zones parallel to the front surface of the wafers and at depths, which agree with the results of the characterization techniques. In these strongly damaged zones, there is a substantial reduction in the phonon intensity, a small shift in wavenumber position, and a large increase in the phonon width. On the basis of a modification of the phonon confinement model that takes under consideration the laser beam profile, the reduction in intensity of scattered light, and the nanocrystallite size distribution from the simulation of the lattice displacements, the main characteristics of the Raman spectra could be reproduced for the random C and O implantations. The results indicate that at a critical doping level, the induced defects and lattice distortions relax by breaking the silicon single crystal into nanocrystallites, thus creating the observed zones of strongly distorted lattice. Copyright © 2014 John Wiley & Sons, Ltd.

Raman mapping of 4‐MeV C and Si channeling implantation of 6H‐SiC

“…Another important factor is the substantially increased roughness of the damaged area, which could be easily observed from both the diffused light and the SEM photos. Here, we will follow the analysis developed in Havel and Baron for SiC and in Kopsalis et al for taking into consideration the size of the laser spot and the reduced scattering from the roughness of the surface. In order to carry out the calculations, we have assumed spot size 1 μm in diameter (Figure S1) and phonon dispersion of the strong E 2 ‐FTO (2/6) mode ν 2 ( q ) = A + [ A 2 − B (1 − cos (π q )] 1/2 with A = 3.18 × 10 5 and B = 1.38 × 10 10 .…”

“…In order to carry out the calculations, we have assumed spot size 1 μm in diameter (Figure S1) and phonon dispersion of the strong E 2 ‐FTO (2/6) mode ν 2 ( q ) = A + [ A 2 − B (1 − cos (π q )] 1/2 with A = 3.18 × 10 5 and B = 1.38 × 10 10 . The scattered intensity is considered proportional to a factor 1 − bexp[−(4π σ / λ ) 2 ], where σ is the mean square roughness and λ is the laser wavelength . We have considered σ to be proportional to the average nanocrystalline size L and L ≈ C/ D β , where C is a constant, D is the amount of displacement, and β is an exponent taken equal to 0.5 from best fit to data.…”

“…High‐energy ion implantation (MeV energy range) is considered to be a promising technique for designing multilayer, three‐dimensional structures deep inside the crystalline material and subsequently increasing the microelectronic chip integration. Moreover, by orienting the ion beam along a crystallographic axis (channeling mode), a deeper implantation in the crystal is expected in comparison with the “random” ion beam solid orientation, as well as a minimization of the induced lattice crystal damage …”

“…The majority of the radiation damage and annealing studies of SiC have employed either ion‐channeling methods based on Rutherford or elastic backscattering spectrometry (EBS/C) or transmission electron microscopy . Micro‐Raman spectroscopy has been used to provide detailed information about the in‐depth distribution of effects induced by high‐energy ion beams . Raman spectroscopy as an optical method has the advantage of being a noncontact analysis tool that requires little or no sample preparation.…”

Integration of correlative Raman microscopy in a dualbeam FIB SEM

“…The study of ion implantation in Si has attracted interest because of the importance of silicon as a semiconductor material, for which ion implantation is generally used as a doping technique though generally a lower ion energy is used . The use of correlated FIB–SEM–Raman is demonstrated by milling a structure in a silicon substrate.…”