• Korean Journal of Materials Research
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• v.26 no.8
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• pp.430-437
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• 2016

Aluminum oxide ($Al_2O_3$) thin films were grown by atomic layer deposition (ALD) using a new Al metalorganic precursor, dimethyl aluminum sec-butoxide ($C_{12}H_{30}Al_2O_2$), and water vapor ($H_2O$) as the reactant at deposition temperatures ranging from 150 to $300^{\circ}C$. The ALD process showed typical self-limited film growth with precursor and reactant pulsing time at $250^{\circ}C$; the growth rate was 0.095 nm/cycle, with no incubation cycle. This is relatively lower and more controllable than the growth rate in the typical $ALD-Al_2O_3$ process, which uses trimethyl aluminum (TMA) and shows a growth rate of 0.11 nm/cycle. The as-deposited $ALD-Al_2O_3$ film was amorphous; X-ray diffraction and transmission electron microscopy confirmed that its amorphous state was maintained even after annealing at $1000^{\circ}C$. The refractive index of the $ALD-Al_2O_3$ films ranged from 1.45 to 1.67; these values were dependent on the deposition temperature. X-ray photoelectron spectroscopy showed that the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ were stoichiometric, with no carbon impurity. The step coverage of the $ALD-Al_2O_3$ film was perfect, at approximately 100%, at the dual trench structure, with an aspect ratio of approximately 6.3 (top opening size of 40 nm). With capacitance-voltage measurements of the $Al/ALD-Al_2O_3/p-Si$ structure, the dielectric constant of the $ALD-Al_2O_3$ films deposited at $250^{\circ}C$ was determined to be ~8.1, with a leakage current density on the order of $10^{-8}A/cm^2$ at 1 V.