Transcript Highly transparent solution processed In-Ga

Highly transparent solution
processed In-Ga-Zn oxide thin
films
Y. Wang • S. W. Liu • X. W. Sun • J. L. Zhao •
G. K. L. Goh • Q. V. Vu • H. Y. Yu
指導教授:林克默博士
學生:董祐成
日期:99/08/16
Outline
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Introduction
Experimental
Result and Discussion
Conclusion
Introduction
1. Transparent oxide semiconductors have attracted
much attention as a potential active channel layer
material for high performance thin film transistors
(TFTs).
2. Compared to the silicon and organic
semiconductors,transparent oxide semiconductors
have unique advantages. They are transparent in the
visible region due to a large bandgap. They also
have a high field effect mobility even for an
amorphous structure due to the s-electron
conduction .
Experimental
1. The precursor solution for IGZO film was
prepared by dissolving 0.1 M of zinc acetate
dehydrate [Zn(OAc)22H2O], 0.1 M indium
chloride and 0.0025 M gallium chloride (the atom
ratio of Ga: In: Zn = 25: 100: 100) in 2methoxyethanol.
2. A 0.1 M monoethanolamine (MEA) was then
added in the precursor solution as a sol–gel
stabilizer.
3. After thoroughly mixing all components, the
solution was stirred at 50 ℃ for 2 h and then aged
for 24 h.
4. IGZO solution was then spin-coated for 2 times on
the prepared substrate at a speed of 3,000 rpm for
30 s and heated at 300 ℃ in the air for 2 min after
each coating.
5. Post-annealing was performed at 400 ~ 800 ℃ for
60 s in oxygen ambient by rapid thermal
annealing (RTA) to remove the residual chemicals
and improve the quality of the IGZO film. The
thickness of the IGZO films was about~30 nm in
our experiment.
Result and Discussion
1. No peaks can be detected from the IGZO films
annealed at lower temperatures (400–600 ℃),
indicating an amorphous structure.
2.The films annealed at higher temperatures (700–
800 ℃) show a weak broad peak, indicating a
nanocrystalline phasebeing formed.
1. the sheet resistance is the highest at an
intermediate annealing temperature (600 ℃).
2. It is worth mentioning that, although
nanocrystalline phase tends to have a lower
mobility through grain boundary scattering, the
mobility may not be directly correlated to the
nanocrystallite size as the crystal phase
(amorphous or nanocrystalline) also affects the
mobility.
3. In our study here, both the mobility and
nanocrystallite size increases with the annealing
temperature.
the IGZO films are highly transparent in the visible
range (400–700 nm) with a transparency of more
than 90% for films annealed with a temperature
higher than 600 ℃. And the transparency is more
than 75% for all films in the range of 300–900 nm.
Conclusion
1. In conclusion, we have fabricated highly
transparent IGZO thin films by solution method
using acetate-and chloratebased precursors.
2.The IGZO films show a phase change from
amorphous to nanocrystalline with the increase of
the post-annealing temperature. Compared to the
nitrate-based IGZO precursor, the chlorate-based
precursor increases the phase change temperature
of IGZO thin films to 600–700 C.
3. The 600 ℃ annealed IGZO films showed a sheet
resistance of 8.4 x 1010 ohm/square and a carrier
concentration of 1.9 x 1013 cm-3, which is the most
suitable for TFT channel in our experiment.
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