Fabrication of on-chip vacuum pump using a silicon nanostructure by metal-assisted chemical etching

We proposed, fabricated, and evaluated an on-chip vacuum pumping device using a nanoporous structure fabricated using metal-assisted chemical etching (MACE) on silicon (Si). The driving principle relies on thermal transpiration, which is generally referred to as a Knudsen pump. MACE can be used to fabricate high-aspect nanostructures of Si, which is advantageous for obtaining a high performance similar to that of a Knudsen pump because the nanochannels and temperature difference are significant components of this principle. The pumping device consists of wafers arranged as follows: glass (300 mu m)/Si (200 mu m)/glass (200 mu m). The glass wafers have small chambers, and the Si wafer has a nanoporous structure with wide channels. One hundred and thirty-two stages (pairs of cool and hot chambers) are cascaded. Vacuum levels are evaluated using a suspended thin diaphragm of Si. The device is fabricated using conventional microfabrication techniques. In the fabricated device, the temperature of the cool and hot sides is maintained at 70 and 230 degrees C. The chamber pressure in the 132nd stage was estimated to be 85.9 kPa, and the evacuation speed was approximately 10 min. (c) 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.