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指導教授：林克默 博士
報告學生：許博淳
報告日期：2011/10/24
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Results and discussion
The crystalline peak at 33°
corresponds to the diffraction
of the (200) plane of the Si
substrate. Except for the peak
from the Si substrate, there is
no prominent peak, which
means that the IGZO thin
films have an amorphous
phase, even at a relatively
high annealing temperature of
600 °C.
•
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Fig. 1. XRD patterns optained from IGZO
thin film annealed from 300 to 600 ℃ in air
for 3hr. The peaks at around 33 ° are from the
Si substrate.
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Results and discussion
Fig. 2. (a and c) High
resolution TEM images
of IGZO thin films
annealed at 300 and 600
°C, respectively. (b and d)
Diffraction patterns of
IGZO thin films
annealed at 300 and 600
°C, respectively. The
marked region in (c)
indicates a nanocrystal
with a size of 5 nm and
the inset is a fast Fourier
transform (FFT) image
of the region with a
crystalline phase.
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Results and discussion
• As shown in the HRTEM results, the IGZO thin films have a
thickness of about 20 nm and an amorphous-like phase.
• In the case of the sample annealed at 600 °C, it is observed that a
very small amount of crystallization occurs with tiny
nanoparticles being formed.
• The region designated in Fig. 2(c) shows a nanoparticle with a
size of about 5 nm and the fast Fourier transform (FFT) of this
region [inset of Fig. 2(c)] confirms that it has a crystalline phase.
However, the low density and small size of these crystals result in
their producing no diffraction peaks in the XRD measurements
and diffraction pattern.
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Results and discussion
Fig. 3 shows the optical
transmittance spectra of the
IGZO thin films annealed at
300 and 600 °C in a
wavelength range of 300–800
nm. These films were spincoated on a Corning 1737
glass substrate and show a
high transparency of over
80% in the visible range at
annealing temperatures of up
to 600 °C.
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Fig. 3. Optical transmittance spectra of the spin
coated IGZO thin films on corning 1737 glass
substrates.
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Results and discussion
•
Fig. 4. Output characteristics of solution processed IGZO TFTs annealed at (a) 300, (b)
400, (c) 500, and (d) 600 °C. Gate voltage is increased from 0 V to 30 V in a 10 V step.
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Results and discussion
• The drain current versus drain to source voltage (ID–VD) output
characteristics of the IGZO TFTs depending on the annealing
temperature, where the gate voltage is varied from 0 to 30 V. The
samples annealed at both 300 and 600 °C exhibit n-type transistor
behavior.
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Results and discussion
The transfer curves are obtained
fromthe drain voltage, showing a
saturated drain current in the output
curves. The threshold voltage (VTH)
can be derived by extrapolating the
square root of the drain current
versus gate voltage (
) curve
in the saturation region. The TFTs
operate in enhancement modewhen
the annealing temperature is 400 °C
or less. On the other hand, the TFTs
annealed at temperatures over 400
°C show depletion mode behavior.
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Fig. 5. Transfer characteristics for
a-IGZO TFTs annealed at different
temperatures.
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Conclusion
• 使用sol-gel製程並進行熱退火的IGZO薄膜層，能成功製造氧
化物薄膜電晶體。
• 退火溫度600℃時IGZO薄膜為非晶相，但還是會觀察到少量
的結晶。
• 熱退火後的IGZO薄膜在可見光範圍內的穿透率達80％以上。
• 隨著退火溫度的升高，使載流子濃度變得更高；由於熱退火
造成的氧空缺，有助於改變TFT的特性。
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Thank you for your attention