Atomic Layer Deposition of Metal Oxides for Emerging Applications

Atomic layer deposition (ALD) is a vapor phase thin film deposition technique that offers excellent control on film thickness and composition and superior conformality. This thesis focuses on the development of a novel portable ALD/Chemical vapor deposition (CVD) hybrid reactor, reactor control architecture and applicability of ALD in different emerging application areas. Design aspects of the portable reactor and its scalable LabVIEW control program are described and discussed in detail. ALD of titanium oxide and CVD of tin oxide were used to test and optimize the hybrid reactor. A novel ethanol based ALD process was developed for selective ALD (SALD) of metal oxides. The SALD process is unique in that no lithography or patterning techniques are needed for selective deposition. SALD of ZrO2 was carried out on copper patterned silicon substrates using ethanol as the oxygen source. Ethanol served as ALD oxygen source on the silicon side and copper reducing agent on the copper side of the substrate. The ethanol based SALD process was able to prevent ALD deposition on copper side up to at least 70 ALD cycles. Ethanol based ALD process was then further studied for deposition of hafnium oxide for high-k applications. HfO2 films showed leakage current density of 5 x 10-8 A/cm2 at 1 V gate bias, which is comparable to films prepared using water based ALD process. ALD of tin oxide was studied for transparent conducting oxide application, often used in optoelectronic devices. The ALD was performed using tin(II)acetylacetonate as a new tin precursor and ozone as the oxygen source. Linear growth rate of 0.1 nm/cycle was achieved within ALD temperature window (175 to 300 oC). Resistivity of the films was in the order of 0.3 Ω-cm. ALD of Sn-doped TiO2 was then studied for photoactivated disinfection of biomedical implants. In this study, atomic layer deposited ultra-thin films (~15 nm) of tin-doped titanium oxide showed excellent antibacterial activity. Up to 98.5% disinfection was achieved within 3 min of low intensity UV exposure at a bacterial killing rate of 18 million/min-cm2 of implant surface.