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1
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- Ping Hou
- Nortel Networks Co.
- Richard Sun
- Angstrom Sun Technologies Inc.
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- Titanium oxide (TiO2)
thin film has been widely used as optical coatings due to its high index
of refraction. It is well known that structures and properties of TiO2
films are highly dependent on the processing techniques. E-beam
evaporation has long been recognized as a practical way of depositing
optical thin films. However, preparing a homogenous TiO2 film
with this technique is still a challenge. One of the difficulties of
getting a structurally uniform TiO2 film lies in the fact of
its low phase transformation temperature. It is vital to find a fast and
non-destructive way to monitor and evaluate the film optical quality. It
is also important to tail the film stress at will to satisfy mechanical
requirements for MEMs devices, such as vertical cavity surface emission
laser (VCSEL). To this end, the stress and structural homogeneity of
e-beam evaporated TiO2 films will be examined and discussed
in this research.
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- TiO2 film stress can be tuned through properly adjusting the
deposition parameters, especially anode current of the ion gun.
- Spectroscopic ellipsometry has been successfully used as a
nondestructive technique to characterize the structural discrepancy of
TiO2 films.
- Three sub-layer model can be used to describe the heterogeneity of
as-deposited TiO2 films, which is caused mainly by the
chamber temperature changes during the deposition.
- With TiO2-SiO2 co-deposition, a homogeneous film
can be produced. At the same time, refractive index can be further tuned
through controlling the ratio of TiO2 to SiO2
fraction in the film.
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Notes
