Delamination owed to environmental stress is a relevant concern in the field of microelectronics packaging. This study is focused on the adhesion of a photosensitive insulator to inorganic passivation layers and metal caps. Peel testing has been combined with confocal laser scanning microscopy to image the bent shape of the peeled layer in situ . Elastic plastic beam theory and finite element analysis have been used to identify a cohesive traction-separation law matching both the work of separation and the peel arm profile. The results indicate that the actual adhesion energy amounts to ~30% of the external work, whereas the rest is dissipated by plasticity. Being the latter related to the curvature of the peel arm during delamination, these results confirm the relevance of in situ imaging in the field of microelectronics reliability.

This work investigates the reciprocal adhesion of Polybenzoxazole (PBO) and silicon nitride (SiN) with a focus on the combined effects of surface chemistry and environmental conditions, i.e., temperature (T) and relative humidity (RH). A set of six samples, including standard and silicon-rich SiN substrates treated with oxygen (O₂) or carbon tetrafluoride (CF₄) plasma, was fabricated and characterized by AFM, XPS, and TEM/EDX to quantify surface roughness and interfacial chemical modifications. Adhesion with PBO was then assessed through nanoindentation both in situ, during ambient control, and ex situ, after aging in a climatic chamber. Compared to PBO adhesion with as-deposited standard and silicon-rich SiN, O₂ plasma treatment was shown to improve adhesion by 13% and 24%, respectively, whereas CF₄ plasma treatment was still beneficial but more limited, improving adhesion by 8% for both substrates. The different effects were ascribed to the formation of a surface oxide layer after O₂ plasma, enhancing chemical affinity and substantially equalizing the adhesion on the two SiN substrates, while CF₄ plasma was impacting adhesion by reducing the substrates’ activity and, thus, increasing the efficiency of the PBO curing procedure. Notably, the adhesion loss with increasing dew point of the ambient (dependent on temperature and relative humidity) was observed across all samples regardless of surface treatment, reinforcing the critical role of absorbed moisture on polymeric film adhesion. However, this trend was observed for all samples only for in situ testing, with a loss of 25% in the critical load of delamination for the most critical environment, while ex situ tests showed a marked recovery of adhesion properties, leading to measurements no longer reflecting the actual state of the samples inside the altered environment. The results presented in this paper highlight the effect of substrate preparation on the adhesion of an organic compound and a substantial difference in environmental control methods for adhesion testing, providing an alternative approach to classical aging treatments and subsequent characterization for qualifying polymer/inorganic interfaces exposed to stressful operational conditions.