Stress silicon nitrides

Numerical thermo-mechanical studies have been performed to improve the robustness of the membrane, addressing buckling and stress concentration (Puigcorb6 et al., 2003). Thermo-mechanical reliability depends on the design and materials used. In general, the membranes made of dielectric materials deposited at a higher temperature (e.g. low-pressure chemical vapor deposition - LPCVD) are more robust. The membrane is usually formed of a stress-compensated stack of thin films of silicon nitride, silicon oxynitride and/or silicon oxide. A heater embedded in between LPCVD low-stress silicon nitride thin films has proven to be robust (Demarne et al.,... 

MACE of tailored nanostructure occurs also by combining lithographic patterning with electroless deposition, with the assistance of a hard, HF-resistant mask, such as polystyrene or low-stress silicon nitride (Chiappini et al. 2010 Asoh et al. 2009). 

A low-stress silicon nitride layer is deposited, lithographically patterned, and etched to allow electrical access to the substrate. 

The main goal of another microhotplate design was the replacement of all CMOS-metal elements within the heated area by materials featuring a better temperature stability. This was accomplished by introducing a novel polysilicon heater layout and a Pt temperature sensor (Sect. 4.3). The Pt-elements had to be passivated for protection and electrical insulation, so that a local deposition of a silicon-nitride passivation through a mask was performed. This silicon-nitride layer also can be varied in its thickness and with regard to its stress characteristics (compressive or tensile). This hotplate allowed for reaching operation temperatures up to 500 °C and it showed a thermal resistance of 7.6 °C/mW. 

The minimum detectable signal for cantilever bending depends on the geometry and the material properties of the cantilever. For a silicon nitride cantilever of 200 pm long and 0.5 pm thick, with E = 8.5 x 1010 N/m2 and v = 0.27, a surface stress of 0.2 mJ/m2 will result in a deflection of 1 nm at the end. Because a cantilever s deflection strongly depends on geometry, the surface stress change, which is directly related to molecular adsorption on the cantilever surface, is a more convenient quantity of the reactions for comparison of various measurements. 

Experiments like those described above have been performed to evaluate sodium ion barrier properties of Hitachi PIQ and DuPont PI 2540 polyimide films. Also included in the comparison were silicon nitride coatings plasma deposited in both tensile and compressive stress modes. The structure of the samples is illustrated in Figure 9. N-type, (111) oriented silicon substrates were cleaned and oxidized in dry oxygen ambient at 1100°C to form a 1060 A Si02 film. Wafers intended for polyimide characterization were coated with an organic silane film (gamma glycidal amino propyl trimethoxysilane) to promote adhesion of the polyimide to the oxide surface. The polyimide resins were spun onto the wafers at speeds to produce final... 

Nagy, P. B. and Adler, L. (1989). On the origin of increased backward radiation from a liquid-solid interface at the Rayleigh angle. J. Acoust. Soc. Am. 85,1355-7. [116] Narita, T., Miura, K., Ishikawa, I., and Ishikawa, T. (1990). Measurement of residual thermal stress and its distribution on silicon nitride ceramics joined to metals with scanning acoustic microscopy. /. Japan. Inst. Metals 54,1142-6. [148]... 

Silicon nitride (95% of a-modification) with 2 wt% of alumina and 5 wt% of yttria as sintering aids (layers with index 1, bulk compressive stress)... 

Figure 5 Stress in silicon nitride films as functions of pressure, frequency and temperature.3 Reprinted by permission of the publisher, The Electrochemical Society, Inc.

Earlier, we reviewed silicon dioxide (thermal) films deposited with added phosphorus to serve as a getter for mobile ion impurities, as a final passivation film. Plasma-enhanced silicon nitride can also be doped with phosphorus.6 Some of the film characteristics have been reviewed, and it was found that the films with 2 to 3% P had the best electrical quality. No measurements of stress or H2 content were reported, so it is not clear that these would be use-able films. 

W.M., Influence of deposition temperature, gas pressure, gas phase composition, and RF frequency on composition and mechanical stress of plasma silicon nitride layer. J. Electrochem. Soc. 132 893 (1985). 

Results on other composite materials are similar to those obtained by Morrell and Ashbee.56 Creep asymmetry has been demonstrated for two grades of siliconized silicon carbide,35,60,61 SiC whisker-reinforced silicon nitride,53 HIPed silicon nitride,29 and vitreous-bonded aluminum oxide.29 Again, stresses required to achieve the same creep rate were at least a factor of two greater in compression than in tension. In two grades of siliconized silicon carbide,35,58-61 the stress exponent changed from 4 at creep rates below... 

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