| dc.description |
A novel high -k gate dielectric material , i .e . , hafnium -doped tantalum oxide (Hf -doped
TaOx ) , has been studied for the application of the future generation metal -oxidesemiconductor
field effect transistor (MOSFET ) . The film's electrical , chemical , and
structural properties were investigated experimentally . The incorporation of Hf into TaOx
impacted the electrical properties . The doping process improved the effective dielectric
constant , reduced the fixed charge density , and increased the dielectric strength . The
leakage current density also decreased with the Hf doping concentration . MOS capacitors
with sub -2 .0 nm equivalent oxide thickness (EOT ) have been achieved with the lightly
Hf -doped TaOx . The low leakage currents and high dielectric constants of the doped films
were explained by their compositions and bond structures . The Hf -doped TaOx film is a
potential high -k gate dielectric for future MOS transistors .
A 5 Ã Â tantalum nitride (TaNx ) interface layer has been inserted between the Hf -doped
TaOx films and the Si substrate to engineer the high -k /Si interface layer formation and
properties . The electrical characterization result shows that the insertion of a 5 Ã Â TaNx
between the doped TaOx films and the Si substrate decreased the film's leakage current density and improved the effective dielectric constant (keffective ) value . The improvement
of these dielectric properties can be attributed to the formation of the TaOxNy interfacial
layer after high temperature O2 annealing . The main drawback of the TaNx interface layer
is the high interface density of states and hysteresis , which needs to be decreased .
Advanced metal nitride gate electrodes , e .g . , tantalum nitride , molybdenum nitride ,
and tungsten nitride , were investigated as the gate electrodes for atomic layer deposition
(ALD ) HfO2 high -k dielectric material . Their physical and electrical properties were
affected by the post metallization annealing (PMA ) treatment conditions . Work functions
of these three gate electrodes are suitable for NMOS applications after 800à °C PMA .
Metal nitrides can be used as the gate electrode materials for the HfO2 high -k film .
The novel high -k gate stack structures studied in this study are promising candidates
to replace the traditional poly -Si -SiO2 gate stack structure for the future CMOS
technology node . |
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