Adhesion properties of polyimide coated stacks: An in-depth analysis of the cross-sectional nanoindentation method

• Published in: Heliyon 2024-12, Vol.10 (24), p.e40967, Article e40967
• Main Authors: Hartleb, Moritz, Imrich, Peter, Zechner, Johannes, Walter, Thomas, Petersmann, Manuel, Khatibi, Golta
• Format: Article
• Language: English
• Subjects: Delamination; Finite element method; Nanoindentation; Polyimide; Thin films
• ISSN: 2405-8440; 2405-8440
• DOI: 10.1016/j.heliyon.2024.e40967

Adhesion at the interface between dissimilar materials in the semiconductor industry is an important topic, but reliable quantitative methods for strongly adhesive or highly plastic layers are hardly available. This study aims to investigate the suitability of the cross-sectional nanoindentation (CSN) method for determination of the critical energy release rate of thin film stacks in the presence of a polyimide layer as a representative structure for such a case. For this purpose, the adhesion of a deliberately weakened Si/SiOx interface in a Si/SiOx/Al/SixNy/polyimide stack is examined by systematic variation of the experimental parameters. This allows for a limitation of the plastic energy dissipated in the polyimide layer during delamination, while still investigating its influences on the overall delamination behavior. The results and evaluability of individual experiments were strongly affected by the geometry of the indenter tip and the distance of indentation to the interface, while other internal control parameters of the nanoindenter were more relevant for ease of the experimental procedure. An optimized choice of the mentioned parameters, 8 μm distance from the deposited layers for the cube-corner tip geometry, and 10 μm for the Berkovich geometry, led to 30 % of evaluable results, considered as high for quantitative adhesion testing of thin films. A multi-stage finite element analysis was developed to consider the effect of plasticity in the polyimide layer. Using this, the critical energy release rates (Gc) of the Si/SiOx interface was determined to be 9.61 J/m2 and 10.85 J/m2 for the cube-corner and Berkovich tip geometries, respectively. This work presents a novel promising way to extend the application fields of the CSN method for the determination of the energy release rate of systems containing layers with a high plasticity. [Display omitted] •A variation and analysis of nanoindentation test parameters and tip geometries allowed to find critical indicators for optimal test conditions.•For varying tip geometry different possible damage behaviors could be identified.•Because of non-elastic effects, a multistep finite element modelling routine was developed to obtain mesh size independent adhesion values.•The average critical energy release rate is 9.61J/m2 and 10.85J/m2 for cube-corner- and Berkovich tip geometry respectively.