The investigation of ion implanted layers by scanning electron microscopy

SEM signals were used to image ion-implanted surfaces and to quantitatively analyze implanted layers. Silicon was used as substrate material for implantation, but some measurements on GaAs are also reported. Various ion species were implanted and the dependence of the signals upon fluence was studied. Electron backscattering and absorbed current were found to be influenced by the radiation damage rather than by the species of implanted ions. The degree of damage could be characterized by absorbed current measurements. The ion fluence necessary to produce amorphous layers was determined for N, P, and As in Si using this technique. This fluence was found to correspond to an energy deposition of 2.8×10²¹ keV/cm³. For the detection of very small amounts of implanted ions by characteristic X-rays, the electron energy must be fitted to the penetration depth of the ions under conditions maintaining reasonable excitation cross sections. The lowest value of the normalized detectability obtained in our measurements was 2.5×10¹³ Ions/cm² for 45 keV phosphorus.