The paper introduces a SU-8 dielectric µ-bridge based polymer MEMS Pirani gauge which can be employed for hermetic characterization of packaged electronic sensors. The µ-bridge structure is adopted due to its simplicity in fabrication and lower footprint, which makes it feasible for heterogeneous integration. Further, the integration of SU-8 polymer with the active thermistor offers superior thermal isolation from the substrate and extends the dynamic range. Before fabricating the actual device, the SU-8 based µ-bridge is optimized for stress-free release. A stress engineering is performed and thermal processing of SU-8 is optimized. The measurement results reveal that the removal of quenching from the baking steps leads to the successful fabrication of freely suspended µ-bridge with SU-8 polymer as a structural layer. A quantitative comparison of the proposed gauge is established by comparing the gauge performance with conventional dielectric materials like silicon dioxide (SiO2), silicon nitride (Si3N4), and aluminum oxide (Al2O3). The fabricated SU-8 polymer-based MEMS Pirani gauge with a 40 µm × 7 µm footprint can be used for hermetic characterization from 30 Pa to 105 Pa and is an ideal candidate for heterogeneous integration.
We demonstrate microelectromechanical system-based flash memory (MEM-FLASH) for multinary bit storage. The MEMS switch integrated with the transistor provides the precise control of the charges on the floating gate. This maneuvering of the charges to 8 different levels provides 3-bit operation even at an elevated temperature of ∼300 °C. The key challenge in the realization of such a memory is the know-how the amount of charge to be transferred to the floating gate to alter the bit state. The charge estimation on the floating gate cannot be performed by direct probing of the device, as this will disturb the original charge values of the floating gate and thus the threshold value. Ergo, an indirect read approach is developed. Furthermore, the cantilever switch is fabricated and tested in a vacuum environment for experimental validation of the approach. The percentage variation from the theoretical to experimental approach is in the adoptable limit of 2%.
This Letter presents a systematic evaluation of the adhesion force between sub-micrometer metal (molybdenum) surfaces in microelectromechanical (MEMS) relays for a range of temperatures (RT to 300 °C). As adhesion force controls whether an electrostatic actuated MEMS relay will detach or remain in contact once the power is turned-off, therefore, it is essential to know the amount of adhesion force present between the interacting electrodes. We present a theoretical scheme that allows direct extraction of the adhesion force from experimentally measured data (ON/OFF-voltage) that can precisely determine the adhesion force from the micro- to nanoregime. Our model identified a clear correlation between the two properties, i.e., ON/OFF-voltage and adhesion force and applicable for any arbitrary material systems. The model is validated by experimental results with varying design parameters. The results confirm that the decreasing nature of pull-OFF voltage (13.9 V to 10.8 V) with increasing temperature ensures a large hysteresis window (∼4.7 V at 300 °C) for n = 3 × 6 and W/L−1 ∼ 6.67, where n is the contact-area dimension and W/L−1 is related to movable electrode geometry. The proposed method can be adopted for the precise designing of various logic relays or memory elements suitable for a wide temperature range.
An electrothermally driven MEMS Pirani gauge with an integrated polymeric (SU-8) thin film is proposed. The structured architecture utilizes the miniaturization advantage of microbridge-type Pirani gauges while combining the lower conduction losses of membrane-based gauges. The integrated polymeric film is highly effective in providing mechanical strength to the metallic resistor and in reducing solid conduction loss to the substrate. Consequently, the dynamic range is extended, and the proposed device shows a wide dynamic range from 40 to 105 Pa. Moreover, biased at 2 mA, the average power consumption of the device is 0.5 mW. Experimental results are in proximity with the simulated results, and the overall footprint of the device is 35 × 7 μm2. The post-CMOS compatible polymer-based Pirani gauge can be used for hermetic characterization for more than three decade-Pa range. The experimentally characterized fusing trend shows that the critical current density for safer operation of the device is 30 mA/ μm2.
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