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

To investigate the phosphorus profile in n-doped Si after the formatio n of buried monocrystalline CoSi2 layers by ion beam synthesis (IBS) e lectrical measurements at PBTs and Schottky diodes and secondary ion m ass spectrometry (SIMS) have been performed. A discrepancy in the drai n current and the pinch-off voltage between dc measurements and simula tions of Si PBTs with buried monocrystalline CoSi2 gates suggests a lo wer doped intermediate layer around the CoSi2 gate fingers. Also a shi ft of intercept voltages to higher values in C-V evaluations of Si/CoS i2 Schottky diodes may be caused by a process-induced change of the do ping profile during IBS. The calculations indicate a decrease or a com pensation of dopants near the CoSi2/Si interface. Investigations by st andard SIMS and the (PCs+)-P-164 molecule-ion technique, which suppres ses 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 fo rmation.