By means of micro structuring the size of a mass spectrometer can be scaled down to about a few cubic centimeters at high precision and reproducibility. Such a miniaturized mass spectrometer is a micro system of very complex nature. It comprises of at least three main parts to be manufactured by micro structuring: an electron source, an ionization region including accelerating and focusing units and a mass analyzer with detector. Since microsystem technologies are 2.5 dimensional - i.e. defined undercuts are difficult to realize - the spectrometer is built of three substrate-layers to achieve the necessary 3D structure. These layers represent the three above mentioned units - each composed of several metal and isolation layers. The substrates are placed cross wise with respect to their electrical connections, so that the top structure can be bonded from below and the bottom structure from the top. The presented layout and processing is adapted to the physical requirements of the system as there are e.g. pressure stages, low capacitance and uncritical assembly, the type of processes and their order are chosen compatible to each other and to the involved materials and structures. This concerns for example the selectivity of etching processes, compatibility of metals, thermal stress, mechanical stress during thick photoresist removal and the thickness of membranes and freestanding structures to survive the mechanical stress imposed during the fabrication.

Date Published: 10 March 1999
PDF: 10 pages
Proc. SPIE 3680, Design, Test, and Microfabrication of MEMS and MOEMS, (10 March 1999); doi: 10.1117/12.341247

Published in SPIE Proceedings Vol. 3680:
Design, Test, and Microfabrication of MEMS and MOEMS
Bernard Courtois; Wolfgang Ehrfeld; Selden B. Crary; Wolfgang Ehrfeld; Hiroyuki Fujita; Jean Michel Karam; Karen W. Markus, Editor(s)