| 초록 |
As semiconductor devices are scaled down for better performance and more functionality, Al2O3 thin films have attracted great interest as an alternative high-k dielectric material in ultra-large-scale integrated devices because of their excellent properties such as its thermal and chemical stability, high dielectric constant (8.6~10), large band gap (~9 eV), and high breakdown electric field(5~10 MV/cm). Recently, Al2O3 thin films as an alternative high-k dielectric for semiconductor devices have increasingly been deposited by atomic layer deposition(ALD), due to the ultrathin thickness of the insulating layer being thinner than 5 nm. However, in order to deposit the ultrathin thickness of the insulating layer being thinner than 5 nm, the process should become more precise and controllable. To our knowledge, although trimethyl aluminium(TMA) has been widely studied as an ALD precursor for Al2O3 and TMA based ALD process is well established, TMA has a difficulty for the ultrathin thickness control, due to the relatively rapid growth rate. Thus, in this study, Al2O3 thin films were grown from a new Al metallorganic precursor and H2O as reactant. Al2O3 thin films were deposited on SiO2 (100nm)/Si and using a travelling wave-type ALD reactor (Lucida–D100, NCD technology, Korea). The deposition temperature was varied from 150 to 300 °C. Low temperature deposition at 140°C was possible with the growth rate of 0.07nm/cycle. When deposition temperature was increased from 150 to 200 °C, the growth rate increased to 0.095nm/cycle. Between 200 and 250 °C, the growth rate was little changed, indicating of the ALD temperature window. This results indicated the growth rate of new ALD-Al2O3 process was relatively low and more controllable as compared to that of TMA-based ALD–Al2O3 process generally showing the growth rate of 1.1nm/cycle, independ of deposition temperature. The refractive index of the Al2O3 thin films monotonically increased from 1.45 to 1.68 with the deposition temperature. SIMS depth profile showed that Al2O3 thin films exhibit good stoichiometry with no impurity incorporation. The step coverage of ALD-Al2O3 thin films were excellent around 100% at 40nm sized structure of dual trench. |
