| AVS 63rd International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF1-ThM |
| Session: | Control and Modeling of Thin Film Growth and Film Characterization |
| Presenter: | Alberto Perrotta, Eindhoven University of Technology, Netherlands |
| Authors: | A. Perrotta, Eindhoven University of Technology, Netherlands W.M.M. Kessels, Eindhoven University of Technology, Netherlands M. Creatore, Eindhoven University of Technology, Netherlands |
| Correspondent: | Click to Email |
Nano-porosity is an intrinsic property of thin films, and it is identified in inorganic layers by the size of rings (e.g., -SiOSi-) and ring termination units (e.g., Si-OH). Porosity control is the key to several technological applications and selected examples are separation membranes, low-k dielectrics, and permeation barrier layers.
In moisture permeation barriers, H2O permeation is known to occur through nano-porosity and the so-called macro-scale defects (from few nm to hundreds of µm). Therefore, the development of methodologies able to follow both permeation paths and predict the quality of a barrier layer are needed.
In this study, an in-depth analysis of nano-porosity in thin films and its impact on their moisture barrier performance are presented.1 Several inorganic layers (SiO2, Al2O3, SiNx) deposited by plasma enhanced-chemical vapor deposition (PE-CVD) and (plasma assisted-) atomic layer deposition (ALD) have been considered. Ellipsometric porosimetry (EP) and electrochemical impedance spectroscopy (EIS) have been adopted as complementary techniques for the analysis of nano-porosity ranging from H2O kinetic diameter (0.27 nm) up to 1 nm. The role of the specific nano-pore range in controlling the intrinsic barrier properties has been disclosed. In detail, absence of porosity with diameter above 0.27 nm led the transition from mediocre (10-4 gm-1day-2) to excellent (10-6 gm-2day-1) H2O barrier properties. Moreover, PA-ALD Al2O3 and SiNx (10-40 nm) layers showed no porosity in the 0.27-1 nm range, and therefore excellent intrinsic barrier properties.
Also, next to nano-porosity, macro-scale defect detection is shown possible by both EIS and EP. Specifically, EIS was shown able to directly detect such defects for barriers deposited on c-Si. With EP, the permeation of probe molecules through barriers deposited on polymers can be followed in time. It is thereby possible to discern diverse events, i.e., filling of nano-porosity in the barrier layer and swelling of the polymer.2 The rate of permeation through the polymer and its swelling has been found to decrease of one order of magnitude upon deposition of porous barriers. The application of a denser layer, impermeable to the probe molecule, showed a further decrease in permeation rate and limited uptake in the polymer. This allowed the isolation of the permeation through macro-scale defects and, thus, their detection.
This research forms part of the research program of the Dutch Polymer Institute (DPI), project #752.
1 Perrotta et al., Microp. Mesop. Mat. 188 (2014) 163; Appl. Mater. Interfaces, 7 (2015) 15968; Plasma Processes Polym. 12 (2015) 968.
2 Perrotta et al., to be submitted.