Sensitivity Enhancement of a PPM Level Capacitive Moisture Sensor

Abstract

Abstract:Measurement of moisture at ppm or ppb level is very difficult and the fabrication of such sensors at low cost is always challenging. High sensitivity is an important parameter for trace level (ppm) humidity sensors. Anelectronic detection circuit for interfacing the humidity sensor with high sensitivity requires a simple hardware circuit with few active devices. The recent trends for increasing the sensitivity include fabricating nanoporous film with a very large surface area. In the present work, the sensitivity of a parallel plate capacitive type sensor with metal oxide sensing film has been significantly improved with an aim to detect moisture from 3 to 100 ppm in the industrial process gases used to fabricate semiconductors and other sensitive electronic devices. The sensitivity has been increased by (i) fabricating a nanoporous film of aluminum oxide using the sol-gel method and (ii) increasing the cross-sectional area of a parallel plate capacitor. A novel double sided capacitive structure has been proposed where two capacitors have been fabricated-one on the top and one on the bottom side of a flat alumina substrate-and then the capacitors are connected in parallel. The structure has twice the sensitivity of a single sensor in the same ppm range but the size of the structure remains unchanged. The important characteristics of the sensors such as the sensitivity (S = ∆C ∆ppm × 100), the response time (t r ), and the recovery time (t c ) are determined and compared with a commercial SHAW, UKdew point meter. The fabricated double sided sensor has comparable sensitivity (S = 100%, t r (s) = 28, t c (s) = 40) with the commercial meter (S = 100.5%, t r (s) = 258) but has a faster response time. The proposed method of sensitivity enhancement is simple, and mass producible.

Aerosol Jet Printing of Silver Lines with A High Aspect Ratio on A Heated Silicon Substrate

“…Currently, there is great interest in the manufacture of low-cost electronic devices using printing technologies [1,2]. The use of these technologies allows the formation of active and passive components by direct deposition of functional materials in the form of nanoparticles on the surface of the substrate without the use of expensive photolithographic masks and stencils [3][4][5][6]. Among the existing printing methods, aerosol jet printing is the most promising technology because it allows the formation of functional elements with a minimum lateral size of up to 10 microns [7][8][9] both on flat and curved substrates [10,11].…”

Printable Highly Stable and Superfast Humidity Sensor Based on Two Dimensional Molybdenum Diselenide

“…Sensitivity of the sensor here is defined by the Eqs. (9) and (10) [49][50][51][52] . Here, Z u , Z l , C u , and C l are the upper and lower limits of the magnitude of impedance and capacitance, respectively, and RH u Figure 7a shows sensitivities calculated for capacitance measurements and Fig.…”

Design and Simulation Investigation of Si3N4 Photonics Circuits for Wideband On-Chip Optical Gas Sensing around 2 µm Optical Wavelength

“…These estimated detection limit values are lower than the occupational exposure limit of 1000 ppm, 25 ppm, and 5000 ppm for CH 4 , NH 3 , and CO 2 recommended by the international environmental standards, respectively [ 64 ]. For water vapor, the resolution limit of a few ppm already makes it compatible with the moisture level required for industrial processes [ 65 ]. Moreover, the estimated detection limit values CH 4 , NH 3 , and CO 2 are compatible with the concentration needed to be regulated in pig houses of ~24, ~12, and ~500 ppm, respectively, as measured by a free space configuration [ 66 ], affirming potential applications of the investigated structure.…”