Epi-less bond etch SOI using MeV ion implantation

The use of keV ion implantation of boron for the bond and etch-back SOI (BESOI) technique is addressed. Ion implantation of boron at 2.5 MeV was used in order to place the boron peak and residual tail of the boron distribution deep enough, so that a region of the original silicon material with acceptably low boron concentration persists near the active-layer-SiO₂ interface. The objective was to determine whether improvements in final uniformity were possible using the MeV implants compared to the more conventional epi-layer technique. Results show that a final thickness of 0.3 μm of single crystal silicon on insulator can be produced with thickness nonuniformity of 28 to 30 nm averaged over 9 points on a 2"×2" area. The final oxidation-stripping steps contributed to most of this nonuniformity. Additional difficulties arose as a result of the extensive oxidation stripping used in the terminal processing steps. Etch pit analysis of the final material revealed substantial oxidation induced stacking faults in the finished material (~300 cm^-2, average length ~50 μm)