Thin Film Synthesis at the Atomic Scale
Key pieces of modern day electronic device technology keep following the trend of down-scaling. Thin film deposition has become of great importance in the semiconductor industry as critical device dimensions have reached the nanometer scale. As down-scaling continues rapidly, device features approach fundamental physical limits. During my doctoral research (at the University of Vienna and Stanford University) my work’s focus was on the characterization of thin films for new high-efficiency applications in solar cells and next-generation dielectrics. The experimental work was particularly focused on atomic layer deposition (ALD), which is a key enabling technique to synthesize high-quality thin films with precise thickness control down to the Angstrom level while staying at low processing temperatures. Unlike in conventional chemical vapor deposition techniques (where there is a continuous flow of precursor gas) in ALD the precursors are introduced sequentially until saturation of the precursor reaction with the surface has occurred and the by-products and remaining precursors are purged out. The key feature that enables this high-quality, conformal growth is the self-limiting nature of the individual half-steps, as illustrated below for the growth of aluminum oxide with the tri-methyl-aluminum (TMA) precursor. Due to the cycle-based nature of this deposition technique thin films can be grown with thickness control down to the atomic level.
During plasma-enhanced ALD (PEALD) a more reactive plasma is used as an oxidant which facilitates lower processing temperatures and higher film quality. However, PEALD typically exhibits less conformal growth of films deposited on complex 3-dimensional substrates with high aspect ratios. My research established processes to deposit thin dielectric films with a record-breaking high dielectric constant and high conformality on complex, high aspect-ratio substrates using PEALD. These metrics are crucial for dynamic RAM applications and resulted in multiple publications and patents with our industrial collaborators. A list of relevant publications with further details are listed below. The list includes my ALD-related work for applications in dielectrics, solar cells, low etching-rate spacer materials, sensors, and catalysis.
- H. J. K. Kim, K. E. Kaplan, P. Schindler, S. Xu, M. M. Winterkorn, D. B. Heinz, T. S. English, J Provine, F. B. Prinz, and T. W. Kenny, Electrical Properties of Ultrathin Platinum films by Plasma Enhanced Atomic Layer Deposition, ACS Appl. Mater. Inter., 11, 9 (2019) 9594–9599 10.1021/acsami.8b21054
- S. Xu, Y. Kim, J. Park, D. Higgins, S.-J. Shen, P. Schindler, D. Thian, J Provine, J. Torgersen, T. Graf, T. Schladt, M. Orazov, B. Liu, T. Jaramillo, and F. B. Prinz, Extending the Limits of Pt/C Catalysts with Passivation-Gas-Incorporated Atomic Layer Deposition, Nature Catalysis, 1 (2018) 624–630 10.1038/s41929-018-0118-1
- P. Schindler*, Y. Kim*, D. Thian, J. An, and F. B. Prinz, Plasma-Enhanced Atomic Layer Deposition of BaTiO3, Scripta Mater., 111 (2016) 106–109 10.1016/j.scriptamat.2015.08.026
- Y. Kim, J Provine, S. P. Walch, J. Park, W. Phuthong, A. L. Dadlani, H. J. Kim, P. Schindler, K. Kim, and F. B. Prinz, Plasma Enhanced Atomic Layer Deposition of SiN-AlN Nanolaminates for Ultra Low Wet Etch Rate in Hydrofluoric Acid, ACS Appl. Mater. Inter., 8, 27 (2016) 17599–17605 10.1021/acsami.6b03194
- J Provine, P. Schindler, Y. Kim, S. P. Walch, H. J. Kim, K. H. Kim and F. B. Prinz, Correlation of Film Density and Wet Etch Rate in Hydrofluoric Acid in Plasma Enhanced Atomic Layer Deposition of Silicon Nitride, AIP Advances, 6, 6 (2016) 065012 10.1063/1.4954238
- Y. Kim, P. Schindler, A. L. Dadlani, S. Acharya, J Provine, J. An, and F. B. Prinz, Plasma-Enhanced Atomic Layer Deposition of Al-Doped Barium Titanate, Acta Mater., 117 (2016) 153–159 10.1016/j.actamat.2016.07.018
- J Provine*, P. Schindler*, J. Torgersen, H. J. Kim, H. P. Karnthaler, and F. B. Prinz, Molecular Oxygen Reactions with Tetrakisdimethylamido-metal Precursors for Atomic Layer Deposition, J. Vac. Sci. Technol. A, 34 (2016) 01A138 10.1116/1.4937991
- S. Acharya*, J. Torgersen*, Y. Kim, J. Park, P. Schindler, A. L. Dadlani, M. Winterkorn, S. Xu, S. Walch, T. Usui, C. Schildknecht, and F. B. Prinz, Atomic Layer Deposition of Barium Oxide and high-k Barium Titanate Thin Films using Novel Pyrrole Based Precursor, J. Mater. Chem. C, 4 (2016) 1945–1952 10.1039/c5tc03561a
- P. Schindler, M. Logar, J Provine, and F. B. Prinz, Enhanced Step Coverage of TiO2 Deposited on High Aspect Ratio Surfaces by Plasma-Enhanced Atomic Layer Deposition, ACS Langmuir, 31, 18 (2015) 5057–5062 10.1021/acs.langmuir.5b00216
- A. L. Dadlani*, O. Trejo*, S. Acharya*, J. Torgersen, I. Petousis, D. Nordlund, R. Sarangi, P. Schindler, and F. B. Prinz, Exploring Local Electronic Structure and Geometric Arrangement of ALD Zn(O,S) Buffer Layers using X-Ray Absorption Spectroscopy, J. Mater. Chem. C, 3 (2015) 12192–12198 10.1039/C5TC02912K
* contributed equally