A monolithic Knudsen pump WITH 20 sccm flow rate using through-wafer ONO channels

• Published in: 2014 IEEE 27th International Conference on Micro Electro Mechanical Systems (MEMS) pp. 112 - 115
• Main Authors: Seungdo An, Yutao Qin, Gianchandani, Yogesh B.
• Format: Conference Proceeding
• Language: English
• Published: IEEE 01.01.2014
• Subjects: Etching; Fabrication; Fluid flow measurement; Heat pumps; Heat sinks; Silicon
• ISSN: 1084-6999
• DOI: 10.1109/MEMSYS.2014.6765586

This paper describes a lithographically microfabricated Knudsen pump for high gas flow. Knudsen pumps operate by thermal transpiration and require no moving parts. To achieve high gas flow, high-density arrays of microchannels (with over 4000 channels/mm 2 ) are used in parallel. These vertically oriented microchannels have 2×120 μm 2 openings surrounded by 0.1 μm-thick silicon oxide-nitride-oxide (ONO) sidewalls. The thin ONO sidewalls provide thermal isolation between a heat sink formed within the Si substrate, and a Cr/Pt heater that provides a temperature bias for thermal transpiration. The Knudsen pump is monolithically microfabricated on a single wafer using a four-mask process. It has a footprint of 8×10 mm 2 . It produces a measured air flow of 20 sccm (i.e., 0.8 sccm/mm 2 ), with typical response times of 0.1-0.4 sec.