| AVS 66th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Monday Sessions |
| Session PS+AS+EM+SS+TF-MoA |
| Session: | Plasma-Surface Interactions |
| Presenter: | Karsten Arts, Eindhoven University of Technology, The Netherlands |
| Authors: | K. Arts, Eindhoven University of Technology, The Netherlands M. Utriainen, VTT Technical Research Centre of Finland R.L. Puurunen, Aalto University School of Chemical Engineering, Finland W.M.M. Kessels, Eindhoven University of Technology, The Netherlands H.C.M. Knoops, Eindhoven University of Technology, The Netherlands |
| Correspondent: | Click to Email |
In this work we measure surface recombination probabilities r of plasma radicals, which is essential for the modeling and understanding of radical-driven plasma processes. Such quantitative information on r is scarcely reported in the literature and typically obtained by difficult and indirect measurement techniques. Here, we determine r using plasma-enhanced atomic layer deposition (ALD) on high aspect ratio (AR) structures, where the AR up to which film growth is obtained gives direct insight into r corresponding to the growth surface. This is demonstrated by measuring the recombination probabilities of O atoms on SiO2, TiO2, Al2O3 and HfO2, revealing a surprisingly strong material-dependence. Aside from studying different materials, our method can for instance be used to investigate the impact of pressure and temperature on r. This can provide valuable information for e.g., device fabrication, plasma source design and simulations, in the context of plasma-enhanced ALD but also relevant outside this field.
For this study, we use microscopic lateral-high-aspect-ratio (LHAR) structures1 supplied by VTT (PillarHall® LHAR4). These chips have extremely high AR trenches (AR<10000) such that film growth is limited up to a certain penetration depth for even the most conformal processes. In the case of plasma ALD, where the film conformality is typically limited by surface recombination,2 we show that the achieved penetration depth can be used to determine r. Furthermore, the LHAR structures allow for comparison of growth behavior with and without an ion component.
These opportunities are demonstrated by plasma ALD of SiO2, TiO2, Al2O3 and HfO2, using an O2/Ar plasma and SiH2(N(C2H5)2)2, Ti(N(CH3)2)4, Al(CH3)3 and HfCp(N(CH3)2)3, respectively, as precursors. It is observed that an exponential increase in plasma exposure time is required to linearly increase the film penetration depth. This relation, which solely depends on r, has been used to determine r=(6±2)⋅10-5, (6±3)⋅10-5, (1-10)⋅10-3 and (0.1-10)⋅10-2 for oxygen radicals on SiO2, TiO2, Al2O3 and HfO2, respectively. Corresponding to these large differences in r, growth of SiO2 and TiO2 penetrated extremely deep up to AR~900, while deposition of Al2O3 and HfO2 was achieved up to AR~90 and AR~40, respectively. This strong material-dependence illustrates the importance of our quantitative research on surface recombination of plasma radicals.