SiC is a candidate material for microelectromechanical and nanoelectromechanical systems, but the high residual stress created during the film grow limits the development of the material for these applications. To understand the stress relaxation mechanism in hetero-epitaxial 3C-SiC films, different micromachined free-standing structures have been realized. In this paper, assisted by finite-element method (FEM), a micromachined planar rotating probe was developed for residual stress analysis to split the stress into the following two components: 1) the gradient residual stress (σ ₁ ) related to the film defects and 2) the uniform stress (σ ₀ ) related to the substrate. Transmission electron microscopy characterization studies about the defect formation and the defect evolution as a function of thickness on 3C-SiC on the Si substrate revealed the problems due to the incorrect linear stress approximation in a heteroepitaxial thin film. With FEM, an exponential approximation of the stress relationship was studied, yielding a better fit with the experimental data. This paper shows that the new approximation of the total residual stress function reduces the actual disagreement between experimental and simulation data.

We reported here a comparative study of PCM cell architectures. The developed architectures are considered in a program/read efficiency framework and in an integration context. The Self-Heating approach is slightly more efficient, owing to heat generation happening directly within GST, but shows hazardous technology implementation with Ge₂Sb₂Te₅, due to high aspect ratios. The heater-based Wall architecture represents the best and easiest solution for PCM from the technology standpoint: it features relaxed aspect ratios and benefits from lots of geometry-based knobs for optimization with slightly higher process complexity and slightly lower efficiency. Strengths and drawbacks of the different architectures are schematically reported in Fig. 14.

The aim of this work is to give an overview on 3C-SiC growth on Si substrates. Starting from the reasons why SiC is considered such an interesting innovative material, with a survey of application already demonstrated, we will present data explaining the most important issues in this hetero-epitaxy system and how the chemical vapor deposition process influences the resulting 3C-SiC film properties. 3C-SiC crystal structure is strongly dependent on the process parameters within the reaction chamber during growth as well as the substrate surface properties. Part of this work is then focused on the main crystallographic defects characterizing the 3C-SiC/Si system and on the resulting wafer bow due to the large misfit between the materials. Defects and wafer bow, are a direct consequence of the large stress generated at the interface. The work closes discussing the encouraging improvements in 3C-SiC crystal quality obtained by the introduction of compliant Si substrates.

The metallized insulating substrates work as mechanical supports for the circuitry of Power Module Packages. Due to their specific functions, substrates for power electronics are made by different materials. The conductive metal layers can assume different functions: the top metal serves as power circuitry routing while the bottom metal improves the mechanical robustness and thermal efficiency. Ceramic layer provides excellent electrical insulation. These features play an essential role in the operation of power modules, which are often operated at high voltage and high current density. The substrates, composed by materials with different thermal expansion coefficients, are subjected to cyclic stresses due to temperature variations induced by operative working conditions. The substrate layouts typically include differences in shape and/or thickness between the top and the bottom side; this generates asymmetrical distributions of stress/strain resulting in overall warpage. The variations of this warpage induce mechanical fatigue during lifetime and represent a limiting factor for reliability. The scope of the presented work is the characterization of the out of plane warpage of Active Metal Brazed substrates (AMB) by means of numerical approach. The elastoplastic properties of metal and ceramic have been measured, evaluating the thermal softening of the copper as well. These characteristics are needed to calculate AMB warpage through Finite Element Models (FEM), simulating the warpage induced by a passive temperature cycling. Warpage computed from numerical model have been benchmarked and validated with optical warpage measurements. The validated numerical model has been developed to optimize the substrate warpage variation during cycling improving the whole package reliability.