The critical impact of temperature gradients on Pt filament failure

Combination of Ceramic Laser Micromachining and Printed Technology as a Way for Rapid Prototyping Semiconductor Gas Sensors

“…In addition to the production flexibility based on 3D modeling, the main advantage of this technological process is the use of ceramic material. Ceramics used for the laser micromilling allow a broadening of the range of working temperatures of the metal oxide sensor for up to 800 • C and can also increase the annealing temperature of the gas-sensitive metal oxide layer up to 1000 • C (in comparison this temperature for silicon technology, which is only 700 • C [28]).…”

Silicon MEMS Thermocatalytic Gas Sensor in Miniature Surface Mounted Device Form

“…In addition, the uniform surface temperature of the microhotplate offers much better selectivity among the target gases with different chemical composition, because of their different activation energies of oxidation. Therefore, the Pt metallization, the geometry, and the structural composition of the microhotplate was designed accordingly to get a decent temperature uniformity as was confirmed by visible pyrometry taken on non-covered microhotplates [23,27]. The heated area has less than ±10 • C temperature difference.…”

“…The microhotplate geometry is also crucial in the sensor response and long-term stability. Moreover, its surface temperature must be uniform in order to minimize the temperature gradient related deterioration phenomena, primarily the electromigration in the filament [27]. In addition, the uniform surface temperature of the microhotplate offers much better selectivity among the target gases with different chemical composition, because of their different activation energies of oxidation.…”

Polycrystalline Diamond Micro‐Hotplates

“…As shown by the visible spectrum micrographs, a uniform faint glow is first visible upon reaching a temperature of 1274 K. This uniformity is in sharp contrast to microscope images taken of meanderbased hotplate structures, where the low thermal conductivity of the dielectric layer often results in significant non-uniform temperature measurements. [11,12] Emission in the visible is also restricted to the radiator element itself and adjoining <50% of the supporting arm, suggesting the temperature along the length of the tether is rapidly reduced before reaching the multi-layer anchor support, preventing the formation of any significant levels of CTE-induced stress. Further increases in temperature result in the emission becoming brighter and completely shrouding the device beneath once exceeding 1673 K as a result of the T 4 Stefan-Boltzmann scaling of the radiated power and color shift owing to the temperature dependence of Wien's law.…”

“…For routinely reaching temperatures of up to 800 K, sufficient for the majority of sensing mechanisms used within solid-state gas detection, [1,9] this heating element is typically fabricated from polycrystalline silicon or platinum. [2,11] Attempts to push poly-Si based devices beyond these temperatures however leads to grain boundary diffusion and a corresponding degradation in device properties. [12] Meanwhile, platinum based devices often require an adhesion layer, adding complexity to the fabrication process, while the comparatively large coefficient of thermal expansion (CTE) of the metal and difference to that of other materials within the stack results in the formation of significant boundary-layer and compressive stress upon heating.…”