In this work iridium silicidation of high dose Ge+ implanted Si layers has been studied. Compositional graded SiGe layers with a Ge peak concentration between 6 at.% and 12 at.% have been fabricated using 200 keV Ge+ ion implantation into (100) Si. A 20 nm thick Ir film was then deposited by e-beam evaporation with thermal reaction being performed to both regrow the implantation damage and form the silicide. The crystal quality of the SiGe layer and its interaction with the Ir film have been studied by cross-sectional Transmission Electron Microscopy (XTEM) and Rutherford Backscattering Spectrometry (RBS).
Solid Phase Epitaxial Growth (SPEG) in the low dose case has produced a defect free SiGe layer with the formation of the IrSi phase. The annealing ambient was found to be critical for the silicidation. For the high dose case, as expected, strain relaxation related defects were observed to nucleate at a depth close to the projected range of the Ge+ implant and to extend up to the surface. A second rapid thermal annealing at higher temperatures, performed in forming gas, consumed most of the defective layer moving the silicide interface closer to the peak of the Ge distribution. A second low dose Ge+ implant following the metal deposition has been found to have a beneficial effect on the quality of the final interface. An amorphizing 500 keV Si+ implant followed by SPEG has finally been used to move the end of range defects far from the interface.