Exploring crystal recovery and dopant activation in coated laser annealing on ion implanted 4H-SiC epitaxial layers

Abstract

In this work an extensive characterization over XeCl multishot laser irradiation was performed at different energy densities and with different thicknesses of graphitic coating superimposed on P and Al implanted 4H-SiC epitaxial layers. It was noted that at 0.6 J/cm(2) the 180 nm coating provides a smooth surface unlike lower thicknesses or uncoated treatments. The mu-Raman investigation showed the crystalline quality as a function of the energy density. Through Medium Angle Annular Dark Field-Scanning Transmission Electron Microscopy (MAADF-STEM) and High Angle Annular Dark Field (HAADF)-STEM investigations, the absence of extended defects and the presence of regions with higher density of carbon interstitials (C-i) was revealed. Circular Transfer Length Method (CTLM) measurements demonstrated how irradiation at 0.9 J/cm(2) succeeded to reach values of (7.28 +/- 1.15) x 10(2) Omega/sq, lower than the findings achieved with furnace treatment at 1650 degrees C. However, electrical characterization carried out through mu-Raman investigation over the Folded Transverse Acoustic (FTA) modes showed consistent activation of the order of 7 x 10(19) cm(-3) at 0.6 J/cm(2) while exhibited CTLM extracted sheet resistance of (3.17 +/- 0.06) x 10(4) Omega/sq. Therefore, this work highlights the contrast between fast processes as the accommodation and ionization of dopant atoms in substitutional positions and slow processes such as the recovery of ion implantation damage. By offering faster processing rates, lower thermal budgets, and high spatial control over the annealing process, laser annealing on 4H-SiC as a post-implantation thermal treatment approach presents several advantages over conventional annealing methods. This study marks a significant progress in comprehending and improving the effectiveness of laser annealing on 4H-SiC.