New Precursors and Chemistry for the Growth of Metal Films by Thermal Atomic Layer Deposition
Pr. Charles H. Winter
Department of Chemistry, Wayne State University, Detroit
Prof. Charles H. Winter obtained his B.S. degree in chemistry from Hope College in 1982. While at Hope College, he was introduced to organometallic chemistry through undergraduate research with Prof. Michael P. Doyle. He then went on to the University of Minnesota, and obtained a doctoral degree in organic and organometallic chemistry in 1986 under the direction of the late Prof. Paul G. Gassman. After an NIH postdoctoral fellowship in organometallic chemistry with Prof. John A. Gladysz at the University of Utah, Prof. Winter joined the faculty at Wayne State University in 1988, where he is currently Professor of Chemistry.
Prof. Winter’s research interests include synthetic inorganic and organometallic chemistry, as well as thin film growth by ALD. Prof. Winter’s laboratory contains threePicosun ALD reactors, allowing precursor synthesis and ALD growth studies to be carried outrapidly. His group seeks to use the power of synthetic chemistry to prepare radically new classes of ALD precursors with chemical reactivity that is designed for the target thin film materials. Current ALD projects in Prof. Winter’s group are directed at the ALD growth of metallic and elementfilms using new organic reducing agents, ALD growth of multimetallic oxides and metal alloys, and atomic layer etching. He has published more than 185 papers and patents.
Atomic layer deposition (ALD)1,2 growth of noble metal (Ru, Os, Rh, Ir, Pd, Pt, Ag, Au) films is conductedan organometallic or metalorganic precursor with O2 or ozone at temperatures of 200 °C or higher.3 These processes afford a metal oxide layer, water, and CO2, and occurby a combustion-like process that removes the organic ligands. At temperatures of ≥ 200 °C, the metal oxide films decompose to metal films. Using this approach, Ru, Os, Rh, Ir, Pd, and Pt and other metal films can be deposited. However, O2 and ozone are powerful oxidants and can damage other materials in microelectronics devices, including W metal, TiN, and TaN layers.4Accordingly, ALD processes based upon strongly oxidizing species are likely to cause integration challenges for films that need to be grown on sensitive substrates. In this talk, we will repost studies aimed at developing to develop alternative, benignchemical reagents for the thermal ALD of noble metal films. We will describe Ru metal ALDemploying (η4-2,3-dimethylbutadiene)(tricarbonyl)ruthenium (Ru(DMBD)(CO)3) and 1,1-dimethylhydrazine. Several other N-based co-reactants will also be described.5 With 1,1-dimethylhydrazine, a growth rate of 0.42 Å/cycle was obtained within an ALD window from 200 to 210 °C. X-ray photoelectron spectroscopy showed>90% Ru metal, with a small amount of N (~7%). Heating these films from 400 to 600 °Cafforded low resistivity, high purity Ru films. The thermal ALD growth of Re metal films will also be described.
1. M. Leskelä and M. Ritala, Angew. Chem. Int. Ed. 42, 5548–5554 (2003).
2. S. M. George, Chem. Rev. 110, 111–131 (2010).
3. J. Hämäläinen, M. Ritala, and M. Leskelä, Chem. Mater. 26, 786–801 (2013).
4. S.-J. Lee, S.-H. Kim, M. Saito, K. Suzuki, S. Nabeya, J. Lee, S. Kim, S. Yeom, and D.-J. Lee, J. Vac. Sci. Technol. A 34, 031509 (2016).
5. S. Cwik, K. N. Woods, M. J. Saly, T. J. Knisley, and C. H. Winter, J. Vac. Sci. Technol. A2019, 31, 012402.