Electrical characterization of thin silicon-on-insulator films doped by means of phosphorus end-terminated polymers

Ex-situ doping of 30 nm thick silicon-on-insulator (SOI) substrates is performed by using polymers terminated with a doping containing moiety. Poly(methylmetachrylate) polymers with a P containing moiety are used to create a phosphorus delta-layer at the interface between the Si device layer and a 10 nm thick SiO2 capping layer deposited on the SOI sample by conventional e-beam evaporation. Drive-in of the P atoms is performed by annealing the samples in a rapid thermal processing (RTP) system at temperatures (TA) ranging from 900 to 1200 degrees C in N2 atmosphere. Annealing time is properly selected to inject a constant P dose of -1 x 1013 cm-2 into the SOI substrate, achieving a uniform dopant concentration throughout the entire Si device layer as verified by Time-of-Flight Secondary Ion Mass Spectroscopy (ToF-SIMS) measurements. Sample resistivity (rho), carrier concentration (ne) and mobility (mu) are determined combining sheet resistance and Hall measurements in the van der Pauw configuration. An average activation rate above 95% is observed at room temperature in the samples annealed at 1000 degrees C for 100 s, suggesting complete activation of the injected dopants. The detection of phos-phorus signal by EPR analysis confirms the extremely high effective concentration of dopants. Low temperature (5-300 K) electrical characterization of a 30 nm thick SOI sample (ne -2.7 x 1018 cm-3 at 300 K) indicates that the evolution of rho, ne and mu values as a function of temperature are perfectly consistent, within the experimental error, with those reported for a P doped bulk Si.

Automated summary

Ex-situ doping of 30 nm thick SOI substrates was achieved by using polymers terminated with a doping containing moiety. The polymers created a phosphorus delta-layer at the interface between the Si device layer and a SiO2 capping layer. P atoms were driven in by annealing the samples in a RTP system at temperatures ranging from 900 to 1200 degrees C. The uniform dopant concentration throughout the entire Si device layer was confirmed by ToF-SIMS measurements.