Electrical activation of B and As implants in Silicon On Insulator (SOI) wafers

MOS devices fabricated on Silicon On Insulator (SOI) substrates show several advantages with respect to those realised on silicon bulk. However, some aspects of the dopant diffusion and activation in SOI are not conclusively clarified yet. With this aim, we have investigated the mechanisms of electrical activation of dopants in very thin (100 or 60 nm) SOI materials. The samples have been doped with As or B, and then spike annealed in the temperature range 450-1125 degreesC. For comparison, selected samples have been pre-amorphised. Spreading resistance probe and four point probe (FPP) measurements have been used as characterisation techniques. The sheet resistance measured in SOI substrates implanted with As is similar to that measured in bulk Si. In contrast, the R-S values measured in BF2 implanted SOI samples are higher than that in bulk Si regardless of the temperature. Electrical profiles measured in SOI and bulk Si substrates implanted with As and BF2 are in agreement with the R-S measurements.