PHOSPHORUS REDISTRIBUTION DURING THE FORMATION OF BURIED COSI2 LAYERS BY ION-BEAM SYNTHESIS

To investigate the phosphorus profile in n-doped Si after the formation of buried monocrystalline CoSi2 layers by ion beam synthesis (IBS) electrical measurements at PBTs and Schottky diodes and secondary ion mass spectrometry (SIMS) have been performed. A discrepancy in the drain current and the pinch-off voltage between dc measurements and simulations of Si PBTs with buried monocrystalline CoSi2 gates suggests a lower doped intermediate layer around the CoSi2 gate fingers. Also a shift of intercept voltages to higher values in C-V evaluations of Si/CoSi2 Schottky diodes may be caused by a process-induced change of the doping profile during IBS. The calculations indicate a decrease or a compensation of dopants near the CoSi2/Si interface. Investigations by standard SIMS and the (PCs+)-P-164 molecule-ion technique, which suppresses the matrix effects considerably, confirm the interpretation of the electrical data in terms of a dopant redistribution by showing a push-out of the phosphorus from the buried CoSi2 layers during silicide formation.