There is considerable interest in
germanium-on-insulator (GeOI) because of its advantages in terms of device
performance and compatibility with silicon processing. In this paper,
fabricating GeOI by hydrogen-induced layer splitting and wafer bonding is discussed.
Hydrogen in germanium exists in molecular form and is prone to outdiffusion,
resulting in a storage-time dependence of blistering. In contrast to the case
of silicon, little effect of substrate doping on blistering is observed in
germanium. Hydrogen implantation in germanium creates both {100}- and
{111}-type microcracks. These two types of platelets are located in the same
region for (111)-oriented wafers, but in different zones for (100) samples.
This variation in distribution explains the smoother splitting of (111)
surfaces than that of (100) surfaces. Hydrogen implantation also introduces a
significant concentration of charged vacancies, which affect dopant diffusion
in the transferred germanium film. Boron, with a negligible Fermi-level dependence,
shows an identical diffusion profile to that of bulk germanium. In contrast,
phosphorus diffusion is enhanced in the fabricated GeOI layers. These results
also shed light on the understanding of dopant diffusion mechanisms in
germanium.
Source:IOPscience
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