Variable Anisotropy in Wet Alkaline Etching of Si Applied for 3-D Structuring

Abstract "“ Anisotropy in silicon wet etching is variable depending on the solution components such as cations and surfactant molecules. Anisotropic etching of Si was conventionally used just for fabricating rectangular recesses and V-grooves on a Si (100) wafer. However, with a TMAH solution containing a surfactant on a level of 0.01%, arbitrary round-shaped recesses and 45-degree-angled facet can be etched on a Si (100) wafer. The working mechanism of the surfactant was investigated. Selec- tive adsorption of the surfactant molecule during etching was observed on Si (110) and (111), while little on (100) surface. We concluded that selectively adsorbed surfactant molecule becomes a barrier for etching. Similarly, the difference in anisot- ropy between KOH and TMAH water solutions is discussed. Complete characterization of etch anisotropy linked with simulation
system, allows fabrication of complicated 3-D microstructures on a silicon wafer.
Bio "“ Prof. Kazuo Sato received BS degree from Yokohama National University in 1970. He worked with Hitachi Ltd. in a period of 1970"“1994. He received his PhD degree from The University of Tokyo in 1982. He had been a professor of Micromachining and MEMS Laboratory, Nagoya University 1994"“2012. He is an emeritus professor of Nagoya University, and a professor at Aichi Institute of Technology since 2012. He started MEMS research in 1983, and published 139 journal papers, 212 conference papers, 34 review articles, and 20 books/book-chapters on MEMS technologies. His research areas are micro/nano-physics in anisotropic etching and mechanical properties of single crystal silicon, as well as applied microsystems such as sensors and actuators.
He co-chaired IEEE MEMS-97 in Nagoya. He is the Editor in Asia of the Journal of Micromechanics and Microengineering (IOP). He is a Fellow of JSME, a Fellow of JSPE, a Senior Member of IEEJ, and a member of IEEE. He is the founding chair of the Micro/Nano Science and Technology Division of JSME established in 2012.