In this work, a high tunable capacitor using a multi-layer dielectric of BZN/BST/BZN is designed and characterized for reconfigurable RF applications. By utilizing a high tunable BST ferroelectric and a low-loss BZN paraelectric thin film, a multi-layer dielectric of BZN/BST/BZN obtained a tunability of 47 % and tanδ of 0.005. The fabricated tunable capacitor on a quartz wafer using this multi-layer dielectric achieved a Q-factor of 10 and tunability of 60 % at 800 MHz and 15 V. Its size is 327 x 642 ㎛2.

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A more in-depth study was conducted on silicon nitride thin films deposited using the space-divided plasma enhance atomic layer deposition (PE-ALD) method. Existing silicon nitride thin films are fabricated using thermal chemical vapor deposition (CVD) at high temperatures of 700 °C or higher with carbon (C)-and chlorine (Cl)-based precursors. However, the high process temperature and the high concentration of C and Cl in films cause a slew of issues for semiconductor integration. In this study, the silicon-nitride thin films have been deposited using the PE-ALD method and an iodine-based precursor to solve these problems. NH 3 and N 2 gases were used as the reactant gases. When N 2 was used as the reactant gas instead of NH 3 , the concentration of the hydrogen (H) impurity was reduced from 19 to 15%. A plasma treatment was used to improve the density and remove the impurities in the thin films; the density of the thin films was confirmed to be 3.21 g/cm 3 , and the H concentration was 11%, indicating that the properties had improved. When a small amount of He gas was added to N 2 , the step coverage properties were improved up to 99.2%. The results of this study confirmed that silicon nitride thin films having superior properties can be produced using iodine-based precursors.

In this study, the effect of deposition temperature of TiN thin films deposited using the thermal atomic layer deposition (ALD) method was investigated. TiCl4 precursor and NH3 reactive gas were used, and the deposition rate, resistivity change, and surface morphology characteristics were compared in the deposition temperature range of 400 °C–600°C. While resistivity decreased to 177 µΩcm as the deposition temperature increased to 600 °C, an increase in surface roughness (Rq) to 0.69 nm and a deterioration in the step coverage were identified. In order to obtain a high-quality TiN thin film with excellent resistivity and step coverage characteristics even at low deposition temperatures, the TiN thin film was post-treated with plasma in a combination of N2/He gas ratio of 3:2 to confirm the change in resistivity. X-ray diffraction analysis confirmed crystallization change in the TiN thin film caused by plasma energy. As a result, the resistivity of the TiN thin film deposited at 400 °C was confirmed to be lowered by about 25%.

In this study, we conducted research on manufacturing molybdenum (Mo) thin films by a thermal atomic layer deposition method using solid MoO2Cl2 as a precursor. Mo thin films are widely used as gate electrodes and electrodes in metal-oxide semiconductor field-effect transistors. Tungsten (W) has primarily been used as a conventional gate electrode, but it suffers from reduced resistivity due to the residual fluorine component generated from the deposition process. Thus, herein, we developed a Mo thin film with low resistivity that can substitute W. The MoO2Cl2 precursor used to deposit the Mo thin film exists in a solid state. For solid precursors, the vapor pressure does not remain constant compared to that of liquid precursors, thereby making it difficult to set process conditions. Furthermore, the use of solid precursors at temperatures 600 °C and above has many limitations. Herein, H2 was used as the reactive gas for the deposition of Mo thin films, and the deposition temperature was increased to 650 °C, which was the maximum processing temperature of the aluminum nitride heater. Additionally, deposition rate, resistivity change, and surface morphology characteristics were compared. While resistivity decreased to 12.9 μΩ∙cm with the increase of deposition temperature from 600 °C to 650 °C, surface roughness (Rq) was increased to 0.560 nm with step coverage of 97%. X-ray diffraction analysis confirmed the crystallization change in the Mo thin film with increasing process temperature, and a certain thickness of the seed layer was required for nucleation on the initial wafer of the Mo thin film. Thus, the molybdenum nitride thin film was deposited after the 4 nm deposition of Mo thin film. This study confirmed that crystallinity of Mo thin films must be increased to reduce their resistivity and that a seed layer for initial nucleation is required.