AVS 63rd International Symposium & Exhibition
    Thin Film Monday Sessions
       Session TF+PS+SE-MoA

Paper TF+PS+SE-MoA6
Mechanical Reliability of PECVD Barrier Films for Flexible Electronics

Monday, November 7, 2016, 3:20 pm, Room 102B

Session: Plasma-based Deposition Techniques and Film Characterization
Presenter: Kyungjin Kim, Georgia Institute of Technology
Authors: K. Kim, Georgia Institute of Technology
A. Singh, Georgia Institute of Technology
H. Luo, Georgia Institute of Technology
T. Zhu, Georgia Institute of Technology
O. Pierron, Georgia Institute of Technology
S. Graham, Georgia Institute of Technology
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The development of PECVD and ALD barrier films have proven to be viable approaches to create barrier films for flexible electronic applications. While much research has focused on the water vapor transport properties of these films, the mechanical reliability during flexural deformation is critical to the performance and durability of these coatings. Overall, the use of the critical onset strain is limiting in trying to define the limits of performance since it ignores time-dependent processes that can occur during mechanical deformation. In this work, we investigate the time-dependent channel crack growth behavior of silicon nitride and ALD barrier films on polyethylene substrates in humid and dry air. The evaluation of the cracking process versus applied strain and load was measuring in-situ using optical and laser scanning confocal microscopy. The results show that crack growth can occur at strains that are much lower than the standard measured onset critical strains. The results of the work show that both polymer relaxation of the PET substrate as well as environmentally assisted crack growth occurs in the films, both in a time dependent manner. Tests in dry air versus tests in humid air show crack growth rates increasing from 100 nm/s to 10 um/s for an applied stress intensity factor of 1.6 MPa.m^0.5. In addition to the dramatic changes in crack growth rates with environmental conditions, larger crack densities were observed in humid environments. This suggests an easier initiation and growth of crack in humidity versus dry air. Overall, the results presented will show the strong link between environment, temperature, and the rate at which cracks grow in barrier films. Finally, the energetics of the crack growth process will be presented as a better metric than onset crack strain to evaluate the mechanical reliability of the barriers for a given application.