(213d) Atomic Layer Deposition for Epitaxial Oxides On Semiconductors

Epitaxial oxides grown on semiconductors are promising new materials for applications in electronics, sensor technology, and the emerging area of spintronics. These applications take advantage of the unique functional properties of crystalline oxides including ferroelectricity, pyroelectricity, piezoelectricity, ferromagnetism, and others. To enable these new applications, it is necessary to integrate crystalline oxides with semiconductors and grow high quality, epitaxial layers. To date, crystalline oxides have only been successfully integrated with semiconductors using molecular beam epitaxy growth methods. Molecular beam epitaxy has the advantages of being a precise growth method for epitaxial layers with in-situ feedback using diffraction methods, but suffers from high capital and operating costs, low throughput, and a need for special operator expertise. It would be a significant advance if growth methods based on industry accepted chemical vapor deposition or atomic layer deposition methods could be developed. Presently, there are no known examples of epitaxial oxides grown on semiconductors by atomic layer deposition or chemical vapor deposition, but in this paper it is argued that the same unique properties of the alkaline earth metals that make epitaxial oxides possible by molecular beam epitaxy are also promising for developing a growth method based on atomic layer deposition. We demonstrate carbonate free growth of alkaline earth metal oxide layers using beta-diketonate precursors with ozone co-reactant and cyclopentadienyl precursors with water co-reactant. The applications of each of these chemistries for epitaxial oxides are discussed. Crystalline oxide/semiconductor surface templates are obtained using an alkaline earth catalyzed oxide desorption process and the nature of the surface reconstructions are discussed. Lastly, the critical issues and remaining challenges for epitaxial oxides by atomic layer deposition and extensions to other semiconductors are discussed.