Development of Microfabricated Cylindrical Ion Trap Mass Spectrometer Arrays

Abstract

A novel approach, in which microelectromechanical systems (MEMS) technology is used for constructing miniature cylindrical ion trap (CIT) mass spectrometer (MS) arrays in silicon (Si), is described. MEMS processes were used to fabricate precise CIT geometries in a stack of Si, SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> . These geometries were then selectively coated with conductive (Cr/Au) layers to obtain a functional CIT array with individual CIT radii (r <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) of 360 mum, half-thickness (z <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) of 351 mum, and aperture size (r <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</sub> ) of 162 mum. Each trap of a 5 times 5 CIT array was operated in the mass selective instability mode to analyze trichloroethylene and perfluorotributylamine at a pressure of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> torr. Mass spectra from individual CITs in the array were obtained using a rasterable electron beam for internal ionization. Investigation of the operation of individual CITs in the array is a critical step toward the understanding of the overall functioning of MS arrays.