Chemical reaction concerns of gate metal with gate dielectric in Ta gate MOS devices: An effect of self-sealing barrier configuration interposed between Ta and SiO2
T. Ushiki et al., Chemical reaction concerns of gate metal with gate dielectric in Ta gate MOS devices: An effect of self-sealing barrier configuration interposed between Ta and SiO2, IEEE DEVICE, 47(11), 2000, pp. 2201-2207
Chemical reaction of gate metal with gate dielectric for Ta gate MOS device
s has been experimentally investigated both by electrical and physical meas
urements: capacitance-voltage (C-V), current-voltage (I-V), transmission el
ectron microscopy (TEM), energy dispersive X-ray (EDX), electron diffractio
n measurements. In spite of the chemical reaction of Ta with SiO2 consuming
similar to1-nm-thick in gate oxide, the interface trap densities of simila
r to2 x 10(10) cm(-2)eV(-1) at midgap and ideal channel mobility characteri
stics have been observed in the Ta gate MOS devices with 5.5-nm-thick therm
al oxide gate dielectric, Considering the experimental data with theoretica
l calculation based on thermodynamics together, a barrier laver model has b
een developed for the Ta gate MOS systems. The physical mechanism involved
is probably self-sealing barrier layer formation resulting from the chemica
l reaction kinetics in the free-energy change of Ta-Si-O system.