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The relationship between the microstructure of silicon nitride and its sensitivity to moisture was studied. The effectiveness of Si-H rich and N-H rich silicon nitride layers was measured under attack from water in vapor and liquid states. For water vapor attack, samples are exposed to vapor at 85 °C with a relative humidity of 85% during 1600 hours; for liquid water attack, samples are dipped in water at 60, 85 and 100 °C for 200 hours. The water resistance of the Si-H rich and N-H rich silicon nitride layers was evaluated by measuring: (i) the thickness of the silicon dioxide formed after their oxidation with water vapor, (ii) the rate of dissolution of the silicon nitride in liquid water and (iii) the corresponding activation of energy. This evaluation was performed by coupling spectroscopic ellipsometry, infra-red and X-ray photoelectron spectrometry analyses. The results revealed that for Si-H rich layer, 10 nm of silicon dioxide was formed during the water vapor attack; for liquid water attack, a high activation energy (0.88 eV) and a low dissolution rate were observed regardless of the water temperature. For N-H rich layers, approximatively 6–8 nm of silicon dioxide was formed and a low activation energy (0.64 eV) with a high dissolution rate were observed. All of these observations lead to the conclusion that the N-H rich layers could be less resistant to moisture because the isoelectronic relationship between Si2N-H and −H2O+ facilitated their deterioration in water. Moreover, a higher rate of nanoporosity for N-H rich layers than Si-H rich layer could complete this hypothesis. [ABSTRACT FROM AUTHOR]

This paper aims at determining thermomechanical stress variations induced by annealed copper filled through-silicon via (TSV) in single crystalline silicon using metal–oxide–semiconductor (MOS) rosette sensors. These eight branches sensors were specifically designed and embedded in a 65-nm CMOS technology test vehicle. An in-house four-point bending tool was employed to calibrate and to extract the six independent piezoresistive coefficients. Through the piezoresistive relations, the stress tensor was evaluated by carrying out electrical measurements on wafer splits. A finite-element approach was also adopted to evaluate numerically the stresses and the expected mobility variations induced by TSV. According to this paper, a large variation of stresses (up to 100 MPa) in the sensor area was estimated, suggesting possible sensor design improvements to better accuracy. A good agreement was obtained between numerical and experimental results, except for the orthoradial component, which was found slightly compressive experimentally. Based on a critical analysis of the experimental–numerical methodology and results detailed in this paper, guidelines are drawn to get better accuracy through the improvement of MOS size and positions as well as recommendations regarding test strategy to overcome process variability. In the longer term, such improvements should lead to the definition of a comprehensive strategy for mechanical stress probing with in situ structures in advanced semiconductor products. [ABSTRACT FROM AUTHOR]

The effect of thermal profile on microstructure is studied in the frame of thin films deposited by inkjet-printing technology. The role of sintering temperature and thermal ramp is particularly investigated. Fast heating ramps exhibit coarse grains and pores, especially when a hybrid microwave curing is performed. This enhanced growth is attributed to the quick activation of densifying sintering regimes without undergoing thermal energy loss at low temperature. Microstructural evolution of various sintered inkjet-printed films is correlated with electrical resistivity and with the Young's modulus determined by nanoindentation. A strong link between those three parameters is highlighted during experiments giving credit to either a surface or a fully volumetric sintering, according to the process. Sintering is then mainly triggered by surface mass transfer or by grain boundary diffusion. Silver thin films with an electrical resistivity 4-5 times higher than the bulk, has been reached in a few minutes with a Young's modulus of 38 GPa. [ABSTRACT FROM AUTHOR]

RF MEMS (Radio Frequency Micro Electro Mechanical System) switches are promising devices but their gold-on-gold contacts, assimilated for this study to a sphere/plane contact, represent a major reliability issue. A first step toward understanding failure mechanisms is to investigate the contact metal microstructure evolution under static and cyclic loading. After static and cyclic loading of sputtered gold thin films under spherical indentation, high-resolution Electron Back Scatter Diffraction (EBSD) is used to investigate the contact area. Grain rotation against {111} fiber texture of 1-μm-thick sputtered gold thin film is a signature of plastic deformation. Grain rotation is observed above 1.6 mN under static loading using a spherical diamond indenter with 50-μm tip radius. The heterogeneity in grain rotation observed corresponds to a greater plastic deformation in the middle of the indent than at the edge. A 30° grain rotation due to cyclic work hardening is observed for a half-million mechanical cycles under 300 μN load using a spherical gold tip (20 μm radius). The same test in hot switching mode induces a grain growth in the contact area. Therefore, thermal effects occurring during hot switching are underlined. [ABSTRACT FROM AUTHOR]