Nitrogen incorporation into high-k gate dielectrics

What effects would take place by doping nitrogen
into high-k gate dielectric like SiON? In this
study, nitrogen incorporation in Hf-based gate
dielectric (HfO2 and HfSiO) has been studied.
Thermal nitridation of Si prior to HfO2 deposition
is one of the methods for incorporating N. However,
it resulted in degraded interface. Thus, top
nitridation was explored to prevent oxygen and boron
penetration into Si substrate while
maintaining high-k/Si interface. As a result,
thermal stability and immunity to boron diffusion
were improved. In addition, 2 times higher drive
current was further enhanced by applying high
temperature forming gas annealing at 600C. To
achieve higher nitrogen concentration at the top,
HfSiON (k~12-16) was used. None of nitrogen in the
upper part of the dielectric diffused to the
interface of HfO2 and Si substrate for anneals up to
800C. Even higher nitrogen concentration at the top
was achieved by NH3 annealing of the gate dielectric
which resulted in EOT 10 Å. The experimental
results of this study suggest that nitrogen profile
engineering for high-k materials is a promising
technique to improve MOSFET performance.

Autorentext

Hag-Ju Cho was born in Korea. He received M.S. degree in Physics
at Seoul National University and Ph.D. degree in Electrical and
Computer Engineering at the University of Texas at Austin in
1994 and 2003, respectively. He joined Samsung Electronics in
1994 and has researched high-k oxides and metal gates for memory
and logic applications.

Klappentext

What effects would take place by doping nitrogen into high-k gate dielectric like SiON? In this study, nitrogen incorporation in Hf-based gate dielectric (HfO2 and HfSiO) has been studied. Thermal nitridation of Si prior to HfO2 deposition is one of the methods for incorporating N. However, it resulted in degraded interface. Thus, top nitridation was explored to prevent oxygen and boron penetration into Si substrate while maintaining high-k/Si interface. As a result, thermal stability and immunity to boron diffusion were improved. In addition, 2 times higher drive current was further enhanced by applying high temperature forming gas annealing at 600C. To achieve higher nitrogen concentration at the top, HfSiON (k~12-16) was used. None of nitrogen in the upper part of the dielectric diffused to the interface of HfO2 and Si substrate for anneals up to 800C. Even higher nitrogen concentration at the top was achieved by NH3 annealing of the gate dielectric which resulted in EOT < 10 Å. The experimental results of this study suggest that nitrogen profile engineering for high-k materials is a promising technique to improve MOSFET performance.