SURFACE-ROUGHNESS OF ION-IMPLANTED [100]SILICON STUDIED BY ATOMIC-FORCE MICROSCOPY

Ion implantation is used in several steps of the integrated circuits fabrication process. As dimensions are being scaled down, it is of interest to gain some knowledge of the possible roughness introduced by implantation. Boron, phosphorus, arsenic and antimony were implanted at 2 X 10(13), 5 X 10(14) and 5 x 10(15) at/cm(2) doses and at 50 and 150 keV. The surface structure has been measured by atomic force microscopy on areas from 0.4 mu m square up to 4 mu m square. The roughness expressed in terms of the root mean square was found to be nearly constant at 0.23 nm and insufficient to characterise these surfaces. The power spectral density was then calculated which very clearly showed the structure differences depending on the size of the implanted ions and their respective doses. Both furnace and rapid thermal annealing were also carried out to analyse their effect on the surface structure after implantation.