An innovative die to wafer stacking is proposed for 3D devices. Known good dices are bonded on a processed wafer thanks to direct bonding. Oxide layers or patterned oxide/copper layers are used as the bonding medium. After a first thinning, a low stress high deposition rate oxide is deposited to embed the dices. A final thinning is then done to recover a flat and smooth surface before the trough silicon vias.

Ellipsometric porosimetry (EP) has recently appeared to be a suitable non‐destructive technique for the characterization of porous ultra low‐κ (ULK) dielectrics. The analysis of ellipsometric spectra of a film during adsorption and desorption cycles of an adsorptive, allows the determination of its open pore fraction, pore size distribution, refractive index and thickness. Several issues are encountered when integrating low‐κ materials as inter‐metal dielectrics (IMD) in the CMOS architecture such as the deposition monitoring, the pore sealing efficiency and the process induced damages. In this study we focus on the capabilities of EP to characterize ULK materials and their integration processes.

Thermoset resins are singular materials in the field of microelectronics. Because they exhibit a high contrast of thermomechanical properties with other integrated materials like oxides, metals or silicon, polymers can threaten the mechanical integrity of stacks. Knowing polymer properties allows manufacturers to foresee the compatibility between materials and improve chipsets reliability. At a bilayer scale, the properties mismatch between the polymer film and the silicon substrate causes an overall curvature of the wafer which evolves with temperature. By comparing the thermally induced curvature of two distinct substrates with the same film, the biaxial modulus and the coefficient of thermal expansion of the film can be determined. This method can not only check the achievement of the polymer cross-linking, but also estimates their relaxation temperatures. In this article, we present the ability of this method to, not only, measure those properties in the glassy state, but also, for the first time, in the rubbery state. We also illustrate the proficiency of this approach in detecting and characterizing two successive glassy states.

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.