Rigidity Enhancement of GeO2 by Y-Doping for Reliable Ge Gate Stacks

The poor reliability of the GeO
₂
/Ge stack is improved by appropriate cation doping [e.g., Yttrium (Y)-doping] into amorphous GeO
₂
as a result of the enhancement of the GeO
₂
network structure stability. In this paper, we discuss the impact of Y-doping on structural modulation of GeO
₂
on a Ge substrate in thermal treatment. By doping a small amount of Y into amorphous GeO
₂
, the crystallization of GeO
₂
to
$\alpha $
-quartz and
$\alpha $
-cristobalite structures is efficiently suppressed without toughening the local Ge-O bond. This is direct evidence of rigidity enhancement of the GeO
₂
tetrahedral network structure by cation doping.