Fabrication and characterization of co-planar type MEMS structures on SiO2 /Si 3 N 4 membrane for gas sensors with dispensing method guided by micromachined wells

• Published in: Journal of electroceramics Vol. 17; no. 2-4; pp. 995 - 998
• Main Authors: Kim, Soo-Ho, Park, Joon-Shik, Lee, In-Gyu
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Nature B.V 01.12.2006
• Subjects: Electrodes; Membranes; Sensors
• ISSN: 1385-3449; 1573-8663
• DOI: 10.1007/s10832-006-9385-3

Issue Title: Special Issue: ICE-2005 International Conference on Electroceramics MEMS structures for micro gas sensors had advantage for lower power consumption, reducing size, and easily making cavity structures. Also, co-planar type MEMS structures (CPMS) for gas sensors with low power consumption heater and dispensed sensing materials were newly proposed and investigated. CPMS, which were formed with micro heater and sensing electrodes at the same layer, to reduce process steps, diffusions between upper layer and lower layer, and thermal differences between the center and the periphery of the sensing layer compared with stacked structure. Dispensing method guided by back-side etched well was good for forming sensing material on sensing electrode and had advantage that various sensing materials could be applied for array type sensors. CPMS were fabricated on four-inch diameter and double side polished (100) silicon wafers and using anisotropic bulk silicon micromachining for membrane formation and etched well. A size of chips with 1.15 mm × 1.15 mm membrane was 4.8 mm × 4.8 mm. And co-planar type sensing electrodes were located in the middle of low stress SiO^sub 2^/Si^sub 3^N^sub 4^ (400 nm /1 μm) membranes. Membranes are thermally isolated from the chip frame because they have low thermal conductivity, generally. Temperatures were measured using IR thermometer with linearly increasing applied power. Power consumption at 400^sup ^C was 150 mW. Membranes of CPMS were withstood up to 730^sup ^C at the power of 350 mW. Characteristics of micro heaters for various heater widths of 50 μm, 75 μm, 100 μm and ratios of membrane dimension to heater dimension were measured. Sensing materials guided by micromachined well were dispensed on sensing electrodes. CPMS were mounted on a TO-8 package. From these results, fabricated and characterized CPMS could be used for applications in portable gas sensors for detection of CO, NO^sub x^, CH^sub x^, H^sub 2^S, and so on.[PUBLICATION ABSTRACT]