Aluminum-oxide(Al2O3) thin films were deposited by electron cyclotron resonance plasma-enhanced atomic layer deposition at room temperature using trimethylaluminum(TMA) as the Al source and O2 plasma as the oxidant. In order to compare our results with those obtained using the conventional thermal ALD method, Al2O3 films were also deposited with TMA and H2O as reactants at 280 oC. The chemical composition and microstructure of the as-deposited Al2O3 films were characterized by X-ray diffraction(XRD), X-ray photo-electric spectroscopy(XPS), atomic force microscopy(AFM) and transmission electron microscopy(TEM). Optical properties of the Al2O3 films were characterized using UV-vis and ellipsometry measurements. Electrical properties were characterized by capacitance-frequency and current-voltage measurements. Using the ECR method, a growth rate of 0.18 nm/cycle was achieved, which is much higher than the growth rate of 0.14 nm/cycle obtained using thermal ALD. Excellent dielectric and insulating properties were demonstrated for both Al2O3 films.

Silicon oxynitride that can be deposited two times faster than general SiNx:H layer was applied to fabricate the passivation protection layer of atomic layer deposition (ALD) Al2O3. The protection layer is deposited by plasma-enhanced chemical vapor deposition to protect Al2O3 passivation layer from a high temperature metallization process for contact firing in screen-printed silicon solar cell. In this study, we studied passivation performance of ALD Al2O3 film as functions of process temperature and RF plasma effect in plasma-enhanced chemical vapor deposition system. Al2O3/SiON stacks coated at 400 oC showed higher lifetime values in the as-stacked state. In contrast, a high quality Al2O3/SiON stack was obtained with a plasma power of 400 W and a capping-deposition temperature of 200 oC after the firing process. The best lifetime was achieved with stack films fired at 850 oC. These results demonstrated the potential of the Al2O3/SiON passivated layer for crystalline silicon solar cells.

We fabricated 10 nm-TiO2 thin films for DSSC (dye sensitized solar cell) electrode application using ALD (atomic layer deposition) method at the low temperatures of 150˚ and 250˚. We characterized the crosssectional microstructure, phase, chemical binding energy, and absorption of the TiO2 using TEM, HRXRD, XPS, and UV-VIS-NIR, respectively. TEM analysis showed a 10 nm-thick flat and uniform TiO2 thin film regardless of the deposition temperatures. Through XPS analysis, it was found that the stoichiometric TiO2 phase was formed and confirmed by measuring main characteristic peaks of Ti 2p1, Ti 2p3, and O 1s indicating the binding energy status. Through UV-VIS-NIR analysis, ALD-TiO2 thin films were found to have a band gap of 3.4 eV resulting in the absorption edges at 360 nm, while the conventional TiO2 films had a band gap of 3.0 eV (rutile)~3.2 eV (anatase) with the absorption edges at 380 nm and 410 nm. Our results implied that the newly proposed nano-thick TiO2 film using an ALD process at 150˚ had almost the same properties as thsose of film at 250˚. Therefore, we confirmed that the ALD-processed TiO2 thin film with nano-thickness formed at low temperatures might be suitable for the electrode process of flexible devices.

A new cost-effective atomic layer deposition (ALD) technique, known as Proximity-Scan ALD (PS-ALD) was developed and its benefits were demonstrated by depositing Al2O3 and HfO2 thin films using TMA and TEMAHf, respectively, as precursors. The system is consisted of two separate injectors for precursors and reactants that are placed near a heated substrate at a proximity of less than 1 cm. The bell-shaped injector chamber separated but close to the substrate forms a local chamber, maintaining higher pressure compared to the rest of chamber. Therefore, a system configuration with a rotating substrate gives the typical sequential deposition process of ALD under a continuous source flow without the need for gas switching. As the pressure required for the deposition is achieved in a small local volume, the need for an expensive metal organic (MO) source is reduced by a factor of approximately 100 concerning the volume ratio of local to total chambers. Under an optimized deposition condition, the deposition rates of Al2O3 and HfO2 were 1.3 Å/cycle and 0.75 Å/cycle, respectively, with dielectric constants of 9.4 and 23. A relatively short cycle time (5~10 sec) due to the lack of the time-consuming "purging and pumping" process and the capability of multi-wafer processing of the proposed technology offer a very high through-put in addition to a lower cost.

Ti[N (C2H5 CH3)2]4 [tetrakis(ethylmethylammino)titanium.TEMAT]와 NH3를 반응가스로 하여 각각 펄스(pulse) 형태로 시분할 주입되는 새로운 박막 증착방법(이하 Cycle-CVD라 함)을 이용하여 TiN박막이 SiO2.기판위에 증착되었다.Cycle-CVD에서 반을로 내로 주입되는 반응가스와 Ar가스는 TEAM 펄스, Ar 펄스,NH3펄스, Ar 펄스의 순서로 시분할주입되었고, 이렇게 차례대로 주입되는 4개의 펄스를 하나의 cycle로 규정하고, Cycle-CVD는 이러한 cycle이 연속하여 반복적으로 주입되도록 설계되었다. 기판온도가 170˚C-210˚C에서는 atomic layer deposition(ALD)특성을 보였고, 200˚C에서 충분한 반응가스의 펄스시간 후에 cycle당 증착된 박막의 두께가 0.6nm/cycle로 포화되는 양상을 보여주었는데, 이는 cycle당 증착된 TiN 박막의 두께가 1.6 monolayer(ML)/cycle에 해당된다. 이와 같이 반등가스의 흡착을 이용ㅇ하여 TiN이 제한된 표면반응만에 의하여 ALD 기구에 의해 증착이 이루어지므로 TiN 박막의 두께는 단지 cycle 횟수만으로 정확하게 제어할 수 있었고, 우수한 step coverage 특성을 얻었다. 또한 반응가스간의 기상반응을 방지함으로써 입자의 발생을 억제할 수 있었고, 상대적으로 낮은 온도임에도 불구하고 4at% 이하의 낮은 탄소함량을 갖는 양호한 특성을 보여주었다.