| Summary: | 碩士 === 國立交通大學 === 材料科學(工程)研究所 === 82 === Al2O3/SiNx dielectric film suitable for large size a-Si:H TFT L
CD have been prepared by anodization and PECVD. Al2O3 layers we
re formed at various pH values and H2O% in the electrolyte, and
treated at various temperatures for 30 min in N2 ambient. The o
ptimal quality for Al2O3 dielectric film was achieved at pH=6,
H2O%=30 in the electrolyte and annealed at 300oC for 30 min. Th
is high quality Al2O3 films have denser structure, low etch rat
e(90 ＊min) and smooth surface morphology after etching. And th
e electrical characteristics of Al2O3 measured from MIM capacit
or show a high breakdown field of 7.8 MV/cm and a low leakage c
urrent density of 10 nA/cm2 at electrical field of 3MV/cm. Furt
hermore, the a-Si:H TFTs with Al gate and with different gate d
ielectrics (Al2O3/SiNx and SiNx) were also fabricated and compa
red. The a-Si:H TFT with Al2O3/SiNx gate dielectric had lower t
hreshold voltage (1.86 V), lower subthreshold swing (1.05 V/dec
), lower off current (32.4 PA), and lower the width of hysteres
is (less than 1.32V) than that with SiNx gate dielectric for ch
annel width 40mm and channel length 50mm. And the annealing of
Al2O3 film also improved the electrical characteristics of the
a-Si:H TFT for threshold voltage (1.76V), subthreshold swing (1
.00V/dec) and off current (4.52pA). Furthermore, the threshold
voltage shift (2.9V) and subthreshold swing shift (1.04V/dec)
of a-Si:H TFT with Al2O3(annealed)/SiNx double-layered gate die
lectric were better than those with Al2O3/SiNx and SiNx gate di
electric under +20V stress for 10000sec.
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