Structural changes of Si surfaces by nitrogen implantation using plasma based ion implantation

Nitrogen ion implantation to Si wafers is carried out by a plasma based ion implantation (PBII) and the compositional and structural changes of the Si surfaces are examined as a function of implantation time by energy dispersive X-ray spectrometer (EDX), Raman and Fourier Transform Infrared (FT-IR) spectroscopy. The implantation time is varied from 10 min to 7 h. From the results of EDX measurements, the N concentration is increased with increasing implantation time up to 1 h, but it is not significantly increased at further increase of implantation time. In the Raman spectra, the sharp peak from Si crystal is decreased in intensity and the small peaks from a-Si and/or a-SiNx appear after N ion implantation. On the other hand, in the FT-IR spectra, a broad peak assigned to Si-N bonds appears after N ion implantation. The result of RBS measurement indicates that the N/Si ratio is approximately 1.3. Judging from these results, it is suggested that a-SiN1.3 is formed as a surface layer on Si wafer by N ion implantation using PBII system.